Money
O Level and IGCSE Mathematics Cheat Sheet – 1.16 Money
Basic Money Operations
| Operation | Method | Example | Answer |
|---|---|---|---|
| Addition | Add amounts directly | $24.75 + $8.60 | $33.35 |
| Subtraction | Subtract smaller from larger | $10.00 − $7.45 | $2.55 |
| Multiplication | Multiply amount by quantity/rate | $12.50 × 3 | $37.50 |
| Division | Divide total by number of items | $45 ÷ 9 | $5.00 |
Written and Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change O Level And IGCSE Mathematics Full Scale Course
Currency Conversion
| Step | Action | Formula | Example |
|---|---|---|---|
| 1 | Identify given rate | 1 USD = £0.78 | — |
| 2 | Multiply to convert to smaller value | Amount × Rate | $200 × 0.78 = £156 |
| 3 | Divide to convert back | Amount ÷ Rate | £500 ÷ 0.78 ≈ $641.03 |
Shopping & Business Applications
| Context | Formula | Example | Result |
|---|---|---|---|
| Discount | Price × (1 − %/100) | $80 at 25% off | $60 |
| Service charge / Tip | Price × (1 + %/100) | $100 + 10% tip | $110 |
| Tax / VAT | Price × (1 + %/100) | $250 + 15% VAT | $287.50 |
Written and Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change O Level And IGCSE Mathematics Full Scale Course
Exam Special Tips
- Always keep units (e.g., $, £, PKR) in every step.
- Keep 4 significant figures in currency conversions until the final step.
- Watch for direction of exchange rate — e.g., $1 = £0.78 is different from £1 = $1.28.
- If question involves multiple steps (e.g., discount + tax), apply changes in correct order.
Common Mistakes & Confusions
| Mistake | Why It’s Wrong | Correct Approach |
|---|---|---|
| Rounding after each step | Accumulates error | Round only final answer |
| Reversing conversion formula | Gives wrong value | Always check if you multiply or divide |
| Ignoring currency format | Can cause misinterpretation | Some currencies (e.g., JPY) have no decimals |