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AYLOTI FORMULA INTELLIGENCE

CAIE O Level, IGCSE, AS & A Level Formula Library

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FORMULA RESULTS

350 formulas across all subjects

Guest progress accuracy
Accounting Foundation New

Financial Statements

Capital

Core & Extended
Capital = Assets − Liabilities

Exam tipUse values at the same date.

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Accounting Foundation New

Financial Statements

Working capital

Core & Extended
Working capital = Current assets − Current liabilities

Exam tipPositive working capital does not automatically mean strong liquidity; consider composition.

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Accounting Foundation New

Income Statement

Cost of sales

Core & Extended
Cost of sales = Opening inventory + Net purchases + Carriage inwards − Closing inventory

Exam tipCarriage inwards belongs in cost of sales; carriage outwards is an expense.

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Accounting Standard New

Depreciation

Straight-line depreciation

Core & Extended
annual depreciation = cost − residual valueuseful life

Exam tipCharge the same annual amount over the asset’s useful life.

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Accounting Challenging New

Depreciation

Reducing-balance depreciation

Core & Extended
depreciation = net book value × rate

Exam tipApply the percentage to the opening net book value each year.

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Accounting Standard New

Adjustments

Provision for doubtful debts

Core & Extended
provision = trade receivables × rate

Exam tipUse adjusted trade receivables after irrecoverable debts are removed.

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Accounting Standard New

Profitability Ratios

Mark-up

Core & Extended
mark-up = gross profitcost of sales × 100%

Exam tipMark-up uses cost of sales as the denominator.

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Accounting Standard New

Profitability Ratios

Profit margin

Core & Extended
profit margin = profit for the yearrevenue × 100%

Exam tipA fall may result from lower gross margin or higher expenses.

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Accounting Challenging New

Profitability Ratios

Return on capital employed

Core & Extended
ROCE = net profit before interestcapital employed × 100%

Exam tipUse profit before interest so returns are compared with all long-term finance.

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Accounting Challenging New

Liquidity Ratios

Liquid (acid-test) ratio

Core & Extended
acid-test ratio = current assets − inventorycurrent liabilities

Exam tipInventory is removed because it may not be quickly converted into cash.

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Accounting Standard New

Efficiency Ratios

Rate of inventory turnover

Core & Extended
inventory turnover = cost of goods soldaverage inventory

Exam tipA higher rate often means inventory is sold more quickly, but context matters.

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Accounting Standard New

Efficiency Ratios

Trade receivables collection period

Core & Extended
receivables days = trade receivablescredit sales × 365

Exam tipCompare with the credit period offered to customers.

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Accounting Standard New

Efficiency Ratios

Trade payables payment period

Core & Extended
payables days = trade payablescredit purchases × 365

Exam tipCompare with the credit period allowed by suppliers.

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Accounting Standard New

Incomplete Records

Profit from capital changes

Core & Extended
profit = closing capital − opening capital + drawings − additional capital

Exam tipAdjust capital changes caused by drawings and fresh investment.

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Accounting Foundation New

Income Statement

Net sales

Core & Extended
net sales = sales − returns inwards

Exam tipReturns inwards reduce revenue.

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Accounting Foundation New

Income Statement

Net purchases

Core & Extended
net purchases = purchases − returns outwards

Exam tipCarriage inwards is added later when calculating cost of sales.

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Accounting Standard New

Inventory

Cost of goods available for sale

Core & Extended
goods available = opening inventory + net purchases + carriage inwards

Exam tipInclude direct purchase costs such as carriage inwards.

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Accounting Standard New

Inventory

Closing inventory from cost of sales

Core & Extended
closing inventory = goods available − cost of sales

Exam tipThis is a rearrangement of the cost-of-sales formula.

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Accounting Standard New

Efficiency Ratios

Inventory holding period

Core & Extended
inventory days = average inventorycost of sales × 365

Exam tipA lower number often indicates faster inventory movement, but context matters.

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Accounting Standard New

Manufacturing Accounts

Prime cost

Core & Extended
prime cost = direct materials + direct labour + direct expenses

Exam tipPrime cost contains only direct production costs.

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Accounting Standard New

Analysis of Financial Statements

Dividend yield

A Level
dividend yield = dividend per share / market price per share × 100%

Exam tipUse consistent units and identify every quantity before substituting.

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Accounting Challenging New

Cost and Management Accounting

Material price variance

A Level
MPV = actual quantity × (standard price − actual price)

Exam tipUse consistent units and identify every quantity before substituting.

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Accounting Challenging New

Cost and Management Accounting

Material usage variance

A Level
MUV = standard price × (standard quantity − actual quantity)

Exam tipUse consistent units and identify every quantity before substituting.

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Business Standard New

Human Resources

Labour turnover

AS & A Level
labour turnover = employees leaving / average number employed × 100%

Exam tipUse consistent units and identify every quantity before substituting.

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Chemistry Foundation New

Stoichiometry

Relative atomic mass

Core & Extended
Ar = Σ(isotope mass × abundance)Σabundance

Exam tipUse all abundances in the same form. If percentages total 100, divide by 100.

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Chemistry Foundation New

Stoichiometry

Relative formula mass

Core & Extended
Mr = ΣAr

Exam tipMultiply each Aᵣ by its subscript before adding.

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Chemistry Foundation New

Stoichiometry

Mass from moles

Core & Extended
m = nMr

Exam tipFirst use the balanced equation to find the required mole ratio.

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Chemistry Standard New

Stoichiometry

Number of particles

Extended
N = nNA

Exam tipState whether particles are atoms, molecules, ions or formula units.

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Chemistry Standard New

Stoichiometry

Moles in solution

Core & Extended
n = cV

Exam tipVolume must be in dm³ when concentration is mol/dm³.

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Chemistry Standard New

Stoichiometry

Mass concentration

Core & Extended
concentration = mass of solutevolume of solution

Exam tipDo not confuse g/dm³ with mol/dm³.

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Chemistry Standard New

Stoichiometry

Gas volume at room conditions

Extended
V = 24n

Exam tipAt room temperature and pressure, 1 mol gas occupies approximately 24 dm³.

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Chemistry Challenging New

Stoichiometry

Atom economy

Extended
atom economy = Mr of desired producttotal Mr of all products × 100%

Exam tipUse coefficients from the balanced equation when totaling product masses.

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Chemistry Standard New

Stoichiometry

Percentage by mass

Extended
% by mass = mass of element in one moleMr of compound × 100%

Exam tipInclude the number of atoms of the element in the formula.

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Chemistry Standard New

Rates of Reaction

Average rate

Core & Extended
rate = change in quantitytime

Exam tipState units from the measured quantity, e.g. cm³/s or g/s.

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Chemistry Standard New

Experimental Techniques

Chromatography Rf value

Core & Extended
Rf = distance moved by substancedistance moved by solvent front

Exam tipRᶠ is between 0 and 1 when measured correctly.

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Chemistry Standard New

Energetics

Thermal energy change

Extended
q = mcΔT

Exam tipFor dilute aqueous solutions, c is often taken as 4.18 J/(g °C) when instructed.

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Chemistry Challenging New

Energetics

Bond energy enthalpy change

Extended
ΔH = ΣE(bonds broken) − ΣE(bonds formed)

Exam tipBreaking bonds absorbs energy; forming bonds releases energy.

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Chemistry Standard New

Solutions

Dilution

Extended
c1V1 = c2V2

Exam tipUse only for dilution where the amount of solute remains unchanged.

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Chemistry Challenging New

Empirical Formula

Empirical formula steps

Extended
moles of each element = massAr

Exam tipDivide all mole values by the smallest, then convert to whole numbers.

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Chemistry Challenging New

Stoichiometry

Reacting mass ratio

Extended
m(A)coefficient A × Mr(A) = m(B)coefficient B × Mr(B)

Exam tipThis combines moles = mass/Mr with the equation ratio.

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Chemistry Standard New

Stoichiometry

Gas volume ratio

Core & Extended
V(A)coefficient A = V(B)coefficient B

Exam tipGas volumes follow the equation ratio when conditions are the same.

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Chemistry Challenging New

Hydrated Salts

Water of crystallisation

Extended
x = moles of H2Omoles of anhydrous salt

Exam tipUse mass lost on heating as the mass of water.

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Chemistry Standard New

Solutions

Molar concentration from mass

Extended
c = mMrV

Exam tipThis combines n = m/Mr and c = n/V.

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Chemistry Standard New

Acid–Base Equilibria

pKa definition

A Level
pKₐ = −log₁₀Kₐ

Exam tipUse consistent units and identify every quantity before substituting.

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Computer Science Standard New

Hash Tables

Load factor

A Level
load factor = occupied slots / total slots

Exam tipUse consistent units and identify every quantity before substituting.

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Computer Science Challenging New

Processor Fundamentals

CPU execution time

A Level
CPU time = instruction count × CPI / clock rate

Exam tipUse consistent units and identify every quantity before substituting.

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Economics Challenging New

Elasticity

Price elasticity of supply

Core & Extended
PES = %Δ quantity supplied%Δ price

Exam tipPES is normally positive because price and supply move in the same direction.

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Economics Challenging New

Elasticity

Income elasticity of demand

Extended
YED = %Δ quantity demanded%Δ income

Exam tipPositive YED indicates a normal good; negative YED indicates an inferior good.

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Economics Challenging New

Elasticity

Cross elasticity of demand

Extended
XED = %Δ demand for X%Δ price of Y

Exam tipPositive XED suggests substitutes; negative XED suggests complements.

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Economics Foundation New

Firms and Production

Average revenue

Core & Extended
AR = TRQ

Exam tipFor a single-price firm, average revenue equals price.

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Economics Foundation New

Firms and Production

Average cost

Core & Extended
AC = TCQ

Exam tipAverage cost may fall as output rises due to economies of scale.

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Economics Standard New

Labour and Productivity

Labour productivity

Core & Extended
productivity = outputlabour input

Exam tipUse the labour-input measure stated in the question.

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Economics Standard New

Macroeconomics

Economic growth rate

Core & Extended
growth rate = new real GDP − old real GDPold real GDP × 100%

Exam tipUse real GDP, not nominal GDP, when measuring changes in output.

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Economics Standard New

Development

Real GDP per head

Core & Extended
real GDP per head = real GDPpopulation

Exam tipIt is an average and does not show income distribution or non-material living standards.

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Economics Challenging New

International Trade

Terms of trade index

Extended
terms of trade = export price indeximport price index × 100

Exam tipA rise is an improvement in the terms of trade, though its overall effect depends on elasticities and…

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Economics Standard New

Exchange Rates

Currency conversion

Core & Extended
domestic currency = foreign currency × exchange rate; foreign currency = domestic currency ÷ exchange rate

Exam tipFirst identify how the exchange rate is quoted. Multiply when converting foreign currency into domestic currency; divide for…

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Economics Challenging New

Labour Markets

Real wage index

Extended
real wage index = money wage indexconsumer price index × 100

Exam tipReal wages rise only when money wages rise faster than prices.

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Economics Challenging New

Macroeconomics

GDP deflator

Extended
GDP deflator = nominal GDPreal GDP × 100

Exam tipThe base year has a deflator of 100.

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Economics Foundation New

Government Finance

Government budget balance

Core & Extended
budget balance = government revenue − government expenditure

Exam tipA negative result is a budget deficit.

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Economics Challenging New

Population

Population growth rate

Extended
growth rate = births − deaths + net migrationpopulation × 100%

Exam tipUse figures from the same time period.

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Economics Standard New

Labour Markets

Labour-force participation rate

Extended
participation rate = labour forceworking-age population × 100%

Exam tipPeople outside the labour force are not counted as unemployed.

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Economics Standard New

Macroeconomics

Marginal propensities

A Level
MPC = ΔC/ΔY; MPS = ΔS/ΔY

Exam tipUse consistent units and identify every quantity before substituting.

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Economics Standard New

Macroeconomic Indicators

Real GDP per head

AS & A Level
real GDP per head = real GDP / population

Exam tipUse consistent units and identify every quantity before substituting.

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Further Mathematics Standard New

Matrices

Eigenvector relation

AS & A Level
Av = λv

Exam tipUse consistent units and identify every quantity before substituting.

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Further Mathematics Challenging New

Hyperbolic Functions

Hyperbolic definitions

A Level
cosh x = (eˣ+e⁻ˣ)/2; sinh x = (eˣ−e⁻ˣ)/2

Exam tipUse consistent units and identify every quantity before substituting.

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Further Mathematics Standard New

Hyperbolic Functions

Hyperbolic identity

A Level
cosh²x − sinh²x = 1

Exam tipUse consistent units and identify every quantity before substituting.

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Further Mathematics Challenging New

Further Mechanics

Projectile trajectory

A Level
y = x tan θ − gx²/(2V²cos²θ)

Exam tipUse consistent units and identify every quantity before substituting.

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Further Mathematics Challenging New

Further Mechanics

Elastic potential energy

A Level
E = λx²/(2l)

Exam tipUse consistent units and identify every quantity before substituting.

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Mathematics Foundation New

Number

Simple interest

Core & Extended
I = PRT100

Exam tipSimple interest is calculated only on the original principal.

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Mathematics Challenging New

Number

Compound growth or decay

Core & Extended
final = initial × (1 ± r)n

Exam tipUse + for growth and − for depreciation. Convert percentage to decimal.

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Mathematics Standard New

Ratio and Proportion

Direct proportion

Core & Extended
y = kx

Exam tipFor direct proportion, y/x is constant and the graph passes through the origin.

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Mathematics Standard New

Ratio and Proportion

Inverse proportion

Extended
y = kx

Exam tipFor inverse proportion, xy is constant.

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Mathematics Challenging New

Algebra

Discriminant

Extended
D = b2 − 4ac

Exam tipD > 0: two real roots; D = 0: one repeated root; D < 0: no real roots.

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Mathematics Standard New

Sequences

Arithmetic sequence nth term

Core & Extended
un = a + (n − 1)d

Exam tipCheck that the difference between consecutive terms is constant.

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Mathematics Challenging New

Sequences

Geometric sequence nth term

Extended
un = arn−1

Exam tipThe ratio between consecutive terms must be constant.

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Mathematics Challenging New

Coordinate Geometry

Perpendicular gradients

Extended
m1m2 = −1

Exam tipThe perpendicular gradient is the negative reciprocal.

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Mathematics Foundation New

Coordinate Geometry

Midpoint

Core & Extended
M = ((x1 + x2)/2, (y1 + y2)/2)

Exam tipAverage the x-coordinates and y-coordinates separately.

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Mathematics Standard New

Coordinate Geometry

Distance between two points

Extended
d = √((x2 − x1)2 + (y2 − y1)2)

Exam tipThis is Pythagoras’ theorem applied to horizontal and vertical changes.

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Mathematics Standard New

Angles and Polygons

Interior angle sum

Core & Extended
sum = (n − 2) × 180°

Exam tipThis gives the total of all interior angles of any polygon.

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Mathematics Standard New

Angles and Polygons

Exterior angle of a regular polygon

Core & Extended
exterior angle = 360°n

Exam tipOne exterior angle plus one interior angle equals 180° for a regular polygon.

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Mathematics Foundation New

Mensuration

Area of a triangle

Core & Extended
A = ½bh

Exam tipThe height must be perpendicular to the chosen base.

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Mathematics Standard New

Mensuration

Area of a parallelogram

Core & Extended
A = bh

Exam tipDo not use the sloping side as the height unless it is perpendicular.

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Mathematics Standard New

Mensuration

Area of a trapezium

Core & Extended
A = ½(a + b)h

Exam tipOnly a and b are the parallel sides.

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Mathematics Foundation New

Mensuration

Circumference of a circle

Core & Extended
C = 2πr = πd

Exam tipDiameter = 2 × radius.

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Mathematics Challenging New

Mensuration

Arc length

Extended
arc length = θ360° × 2πr

Exam tipUse the central angle of the sector.

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Mathematics Challenging New

Mensuration

Area of a sector

Extended
sector area = θ360° × πr2

Exam tipA semicircle uses θ = 180°; a quarter-circle uses 90°.

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Mathematics Standard New

Mensuration

Volume of a prism

Core & Extended
V = Al

Exam tipThe cross-section must be constant along the prism.

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Mathematics Standard New

Mensuration

Volume of a pyramid

Core & Extended
V = ⅓Ah

Exam tipUse perpendicular height, not a sloping edge.

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Mathematics Standard New

Mensuration

Volume of a cylinder

Core & Extended
V = πr2h

Exam tipCylinder volume = circular cross-section × length.

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Mathematics Standard New

Mensuration

Curved surface area of a cylinder

Core & Extended
A = 2πrh

Exam tipTotal surface area also includes two circles: 2πr².

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Mathematics Challenging New

Mensuration

Volume of a cone

Core & Extended
V = ⅓πr2h

Exam tipA cone has one-third the volume of a cylinder with the same base and height.

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Mathematics Standard New

Mensuration

Curved surface area of a cone

Core & Extended
A = πrl

Exam tipUse slant height l, not vertical height h.

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Mathematics Standard New

Mensuration

Volume of a sphere

Core & Extended
V = 43πr3

Exam tipUse 4/3 × π × r³. Do not confuse volume with surface area.

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Mathematics Challenging New

Mensuration

Surface area of a sphere

Core & Extended
A = 4πr2

Exam tipA hemisphere’s curved area is 2πr²; add πr² if the circular base is included.

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Mathematics Standard New

Trigonometry

Sine ratio

Core & Extended
sin θ = oppositehypotenuse

Exam tipUse only in a right-angled triangle. Label sides relative to θ.

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Mathematics Standard New

Trigonometry

Cosine ratio

Core & Extended
cos θ = adjacenthypotenuse

Exam tipThe adjacent side is next to θ but is not the hypotenuse.

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Mathematics Standard New

Trigonometry

Tangent ratio

Core & Extended
tan θ = oppositeadjacent

Exam tipUse inverse tan to find an angle.

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Mathematics Challenging New

Trigonometry

Area using sine

Extended
A = ½ab sin C

Exam tipThe angle must lie between the two chosen sides.

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Mathematics Standard New

Similarity

Area scale factor

Core & Extended
area factor = k2

Exam tipAreas change with the square of the linear scale factor.

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Mathematics Standard New

Similarity

Volume scale factor

Core & Extended
volume factor = k3

Exam tipVolumes change with the cube of the linear scale factor.

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Mathematics Standard New

Statistics

Mean from a frequency table

Core & Extended
mean = ΣfxΣf

Exam tipFor grouped data, use class midpoints, so the answer is an estimate.

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Mathematics Challenging New

Statistics

Frequency density

Extended
frequency density = frequencyclass width

Exam tipHistogram bar area represents frequency.

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Mathematics Foundation New

Probability

Complement rule

Core & Extended
P(not A) = 1 − P(A)

Exam tipAll probabilities lie between 0 and 1.

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Mathematics Challenging New

Probability

Independent events

Extended
P(A and B) = P(A) × P(B)

Exam tipMultiply along branches of a probability tree.

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Mathematics Standard New

Probability

Mutually exclusive events

Extended
P(A or B) = P(A) + P(B)

Exam tipAdd only when A and B cannot happen together.

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Mathematics Foundation New

Percentages

Loss percentage

Core & Extended
loss % = losscost price × 100%

Exam tipLoss percentage is also based on cost price.

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Mathematics Standard New

Finance

Amount with simple interest

Core & Extended
A = P(1 + rt)

Exam tipUse r = 0.06 for 6%.

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Mathematics Foundation New

Standard Form

Multiplying standard form

Core & Extended
(a × 10m)(b × 10n) = ab × 10m+n

Exam tipMultiply the numbers and add the powers, then normalise the answer.

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Mathematics Foundation New

Standard Form

Dividing standard form

Core & Extended
a × 10mb × 10n = ab × 10m−n

Exam tipDivide the coefficients and subtract the powers.

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Mathematics Challenging New

Algebra

Completing the square identity

Extended
x2 + bx = (x + b2)2 − (b2)2

Exam tipTake half the coefficient of x.

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Mathematics Foundation New

Coordinate Geometry

Parallel line gradients

Core & Extended
m1 = m2

Exam tipParallel lines have the same gradient.

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Mathematics Challenging New

Coordinate Geometry

Gradient from angle

Extended
m = tan θ

Exam tipCheck how the angle is measured before using tangent.

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Mathematics Standard New

Pythagoras

Three-dimensional Pythagoras

Core & Extended
d = √(l2 + w2 + h2)

Exam tipAll three dimensions must use the same unit.

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Mathematics Foundation New

Angles and Polygons

Number of sides from exterior angle

Core & Extended
n = 360°exterior angle

Exam tipThis applies to a regular polygon.

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Mathematics Foundation New

Mensuration

Area of a rectangle

Core & Extended
A = lw

Exam tipUse perpendicular side lengths.

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Mathematics Standard New

Mensuration

Area of a rhombus or kite

Core & Extended
A = 12d1d2

Exam tipThe formula uses the two diagonals, not two sides.

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Mathematics Foundation New

Mensuration

Volume of a cuboid

Core & Extended
V = lwh

Exam tipUse the same unit for all dimensions.

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Mathematics Standard New

Mensuration

Total surface area of a cone

Extended
A = πr2 + πrl

Exam tipUse slant height for the curved surface, not vertical height.

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Mathematics Challenging New

Mensuration

Area of a circular segment

Extended
segment area = sector area − triangle area

Exam tipUse the triangle formed by the two radii and the chord.

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Mathematics Foundation New

Statistics

Range

Core & Extended
range = maximum − minimum

Exam tipThe range measures spread but ignores all middle values.

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Mathematics Challenging New

Probability

Conditional probability

Extended
P(A | B) = P(A ∩ B)P(B)

Exam tipThe sample space is restricted to event B.

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Mathematics Standard New

Pure Mathematics

Finite geometric series

AS & A Level
Sₙ = a(1 − rⁿ)/(1 − r)

Exam tipUse consistent units and identify every quantity before substituting.

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Mathematics Standard New

Pure Mathematics

Binomial expansion

AS & A Level
(a + b)ⁿ = Σ ⁿCᵣ aⁿ⁻ʳbʳ

Exam tipFor rational powers use the generalized expansion and its validity condition.

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Mathematics Standard New

Algebra

Sum and product of quadratic roots

AS & A Level
α + β = −b/a; αβ = c/a

Exam tipUse consistent units and identify every quantity before substituting.

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Mathematics Standard New

Differentiation

Quotient rule

AS & A Level
d(u/v)/dx = [v(du/dx) − u(dv/dx)]/v²

Exam tipUse consistent units and identify every quantity before substituting.

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Mathematics Standard New

Differentiation

Exponential and logarithmic derivatives

AS & A Level
d(eˣ)/dx = eˣ; d(ln x)/dx = 1/x

Exam tipUse consistent units and identify every quantity before substituting.

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Mathematics Standard New

Integration

Logarithmic integral

AS & A Level
∫1/x dx = ln|x| + C

Exam tipUse consistent units and identify every quantity before substituting.

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Mathematics Standard New

Integration

Exponential and trigonometric integrals

A Level
∫eˣdx=eˣ+C; ∫sin x dx=−cos x+C; ∫cos x dx=sin x+C

Exam tipUse consistent units and identify every quantity before substituting.

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Mathematics Standard New

Probability & Statistics

Binomial mean and variance

AS & A Level
E(X)=np; Var(X)=np(1−p)

Exam tipUse consistent units and identify every quantity before substituting.

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Mathematics Challenging New

Probability & Statistics

Poisson probability

A Level
P(X=r) = e⁻λ λʳ/r!

Exam tipUse consistent units and identify every quantity before substituting.

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Physics Standard New

Motion

Average velocity

Core & Extended
v = ΔxΔt

Exam tipVelocity uses displacement, not total path length. Direction matters.

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Physics Standard New

Motion

Distance from a speed–time graph

Core & Extended
distance = area under the speed–time graph

Exam tipSplit the area into rectangles and triangles when needed.

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Physics Standard New

Motion

Acceleration from a velocity–time graph

Extended
a = ΔvΔt

Exam tipAcceleration is the gradient. Use a large triangle on a straight section.

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Physics Foundation New

Forces

Weight

Core & Extended
W = mg

Exam tipMass is measured in kg; weight is a force measured in N.

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Physics Standard New

Forces

Hooke’s law

Core & Extended
F = kx

Exam tipValid only up to the limit of proportionality. Extension = stretched length − original length.

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Physics Standard New

Forces

Moment of a force

Core & Extended
moment = Fd

Exam tipThe distance must be perpendicular to the line of action of the force.

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Physics Standard New

Forces

Principle of moments

Core & Extended
clockwise moments = anticlockwise moments

Exam tipUse this only when the object is in rotational equilibrium.

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Physics Standard New

Pressure

Pressure in a liquid

Extended
p = ρgh

Exam tipThis gives pressure caused by the liquid column. Use vertical depth.

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Physics Standard New

Momentum

Impulse

Extended
FΔt = Δp

Exam tipIncreasing collision time reduces average force for the same momentum change.

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Physics Challenging New

Momentum

Conservation of momentum

Extended
total p before = total p after

Exam tipChoose one direction as positive and keep signs consistent.

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Physics Standard New

Energy, Work and Power

Power from energy

Core & Extended
P = ΔEt

Exam tipUse this form when energy rather than work is given.

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Physics Standard New

Energy, Work and Power

Power efficiency

Extended
efficiency = useful power outputtotal power input × 100%

Exam tipUse power values only; do not mix power with energy.

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Physics Challenging New

Thermal Physics

Specific heat capacity

Extended
Q = mcΔT

Exam tipUse temperature change, not final temperature. Match mass units to c.

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Physics Challenging New

Thermal Physics

Specific latent heat

Extended
Q = mL

Exam tipDuring a change of state, temperature remains constant.

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Physics Foundation New

Waves

Frequency and period

Core & Extended
f = 1T

Exam tipPeriod is the time for one complete oscillation.

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Physics Standard New

Light

Refractive index

Extended
n = sin isin r

Exam tipAngles are measured from the normal, not the surface.

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Light

Critical angle

Extended
n = 1sin c

Exam tipThis form applies when light travels from the material into air.

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Physics Standard New

Light

Magnification

Core & Extended
magnification = image heightobject height

Exam tipUse the same units for image height and object height.

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Physics Foundation New

Electricity

Charge flow

Core & Extended
Q = It

Exam tipConvert minutes to seconds before substituting.

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Physics Standard New

Electricity

Resistors in series

Core & Extended
RT = R1 + R2 + …

Exam tipSeries resistance is always greater than any individual resistance.

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Electricity

Resistors in parallel

Extended
1RT = 1R1 + 1R2 + …

Exam tipParallel resistance is smaller than the smallest branch resistance.

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Physics Standard New

Electricity

Power in a resistor

Extended
P = I2R

Exam tipUse when current and resistance are known.

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Physics Standard New

Electricity

Power from voltage and resistance

Extended
P = V2R

Exam tipUse when voltage and resistance are known.

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Physics Standard New

Electricity

Electrical energy

Core & Extended
E = VIt

Exam tipThis is equivalent to E = Pt.

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Physics Challenging New

Electromagnetic Effects

Transformer turns ratio

Extended
VpVs = NpNs

Exam tipA step-up transformer has more turns on the secondary coil.

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Physics Standard New

Electromagnetic Effects

Ideal transformer power

Extended
VpIp = VsIs

Exam tipFor an ideal transformer, input power equals output power.

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Physics Standard New

Electromagnetic Effects

Force on a current-carrying conductor

Extended
F = BIL

Exam tipApplies when the conductor is perpendicular to the magnetic field.

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Physics Standard New

Nuclear Physics

Corrected count rate

Core & Extended
corrected count rate = measured count rate − background count rate

Exam tipAlways subtract background count measured over the same time interval.

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Nuclear Physics

Half-life decay

Core & Extended
N = N0(½)n

Exam tipn = elapsed time ÷ half-life. This model is useful for repeated halving.

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Space Physics

Hubble’s law

Extended
v = H0d

Exam tipKeep distance in megaparsecs if H₀ is given in km/s/Mpc.

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Physics Challenging New

Energy, Work and Power

Elastic potential energy

Extended
Ee = 12kx2

Exam tipThe extension is squared, so convert it to metres before squaring.

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Physics Foundation New

Simple Machines

Mechanical advantage

Core & Extended
MA = loadeffort

Exam tipMechanical advantage is a force ratio and has no unit.

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Physics Standard New

Simple Machines

Velocity ratio

Core & Extended
VR = distance moved by effortdistance moved by load

Exam tipUse distances moved in the same unit.

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Physics Standard New

Simple Machines

Machine efficiency

Core & Extended
efficiency = MAVR × 100%

Exam tipA real machine normally has an efficiency below 100%.

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Physics Foundation New

Thermal Physics

Celsius to kelvin

Core & Extended
T = θ + 273

Exam tipKelvin temperatures do not use the degree symbol.

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Physics Foundation New

Waves

Wavelength from wave speed

Core & Extended
λ = vf

Exam tipThis is the wave-speed equation rearranged for wavelength.

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Physics Challenging New

Space Physics

Orbital speed

Extended
v = 2πrT

Exam tipThe distance travelled in one circular orbit is 2πr.

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Physics Standard New

Deformation

Strain

AS & A Level
strain = ΔL/L

Exam tipUse consistent units and identify every quantity before substituting.

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Physics Standard New

Waves

Wave intensity

AS & A Level
I = P/A

Exam tipUse consistent units and identify every quantity before substituting.

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Physics Standard New

Gravitational Fields

Gravitational potential

A Level
φ = −GM/r

Exam tipUse consistent units and identify every quantity before substituting.

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Physics Challenging New

Quantum Physics

Photoelectric equation

A Level
hf = Φ + ½mvₘₐₓ²

Exam tipUse consistent units and identify every quantity before substituting.

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