Introduction To Probability (Copy)
1.
A coin is tossed once. Find P(Head).
2.
A coin is tossed once. Find P(not a Tail).
3.
A die is rolled. Find P(rolling a 4).
4.
A die is rolled. Find P(not rolling a 6).
5.
A box contains 5 red balls and 3 blue balls. One ball is chosen at random. Find P(red).
6.
From Q5, find P(blue).
7.
From Q5, find P(not red).
8.
There are 20 students: 12 boys and 8 girls. A student is chosen. Find P(choosing a girl).
9.
From Q8, find P(choosing not a girl).
10.
A bag has 10 marbles, 3 are green. One marble is taken. Find P(green).
11.
From Q10, find P(not green).
12.
A card is drawn from a standard deck of 52 cards. Find P(drawing an Ace).
13.
From Q12, find P(not an Ace).
14.
In a survey, 70% of people like tea. Find P(a person does not like tea).
15.
The probability it rains tomorrow is 0.3. Find P(no rain).
16.
A spinner has 5 equal sections labelled A, B, C, D, E. Find P(landing on C).
17.
From Q16, find P(not landing on C).
18.
A box contains 4 red, 6 yellow, and 10 green pens. A pen is chosen at random. Find P(red).
19.
From Q18, find P(yellow).
20.
From Q18, find P(not green).
21.
The probability a bus arrives on time is 0.85. Find P(it is late).
22.
A school has 400 students. 240 study science. Find P(a student chosen studies science).
23.
From Q22, find P(a student chosen does not study science).
24.
A coin is tossed twice. Write the sample space. Find P(getting 2 Heads).
25.
From Q24, find P(getting at least one Head).
26.
The probability that a machine works = 0.92. Find P(it fails).
27.
A jar has 12 black counters and 18 white counters. One is picked. Find P(white).
28.
From Q27, find P(black).
29.
A number is chosen at random from 1 to 20. Find P(the number is even).
30.
From Q29, find P(the number is not even).
1.
P(Head) = ½.
Coin has 2 equally likely outcomes.
2.
P(not Tail) = 1 − P(Tail) = 1 − ½ = ½.
3.
P(rolling a 4) = 1/6.
One “4” out of 6 outcomes.
4.
P(not 6) = 1 − 1/6 = 5/6.
5.
Total = 5+3=8.
P(red) = 5/8.
6.
P(blue) = 3/8.
7.
P(not red) = P(blue) = 3/8.
8.
P(girl) = 8/20 = 2/5.
9.
P(not girl) = P(boy) = 12/20 = 3/5.
10.
Total = 10. Green=3.
P(green) = 3/10.
11.
P(not green) = 1 − 3/10 = 7/10.
12.
Aces = 4. Total=52.
P(Ace) = 4/52 = 1/13.
13.
P(not Ace) = 1 − 1/13 = 12/13.
14.
P(not tea) = 1 − 0.7 = 0.3 (or 30%).
15.
P(no rain) = 1 − 0.3 = 0.7.
16.
P(C) = 1/5.
17.
P(not C) = 4/5.
18.
Total = 4+6+10=20.
P(red) = 4/20 = 1/5.
19.
P(yellow) = 6/20 = 3/10.
20.
P(not green) = (4+6)/20 = 10/20 = ½.
21.
P(late) = 1 − 0.85 = 0.15.
22.
P(science) = 240/400 = 3/5.
23.
P(not science) = 160/400 = 2/5.
24.
Sample space: {HH, HT, TH, TT}.
P(2 Heads) = 1/4.
25.
At least one Head = {HH, HT, TH}.
P = 3/4.
26.
P(fails) = 1 − 0.92 = 0.08.
27.
Total = 12+18=30.
P(white) = 18/30 = 3/5.
28.
P(black) = 12/30 = 2/5.
29.
Even numbers from 1–20 = 10.
P(even) = 10/20 = ½.
30.
P(not even) = 1 − ½ = ½.