Bluebook SAT Test Probability and Conditional Probability 11

Question 1

A random number is selected from 1 to 30. What is the probability that it is divisible by 4?

Accepted Answer

7/30

Answer

Multiples of 4 in 1–30: 4, 8, 12, 16, 20, 24, 28 — that's 7 numbers; P = 7/30.

Question 2

The table below shows 400 survey respondents by age group and whether they voted.

Voted   Did Not Vote
Under 30     80        120
30 and over 160         40

What is the probability that a randomly chosen voter is under 30?

Accepted Answer

1/3

Answer

Total voters = 80 + 160 = 240; P(under 30 | voted) = 80/240 = 1/3.

Question 3

P(A) = 0.45, P(B) = 0.30, and P(A and B) = 0.15. What is P(A or B)?

Accepted Answer

0.60

Answer

P(A or B) = 0.45 + 0.30 − 0.15 = 0.60.

Question 4

A jar has 5 orange and 5 purple jellybeans. Three are drawn one at a time without replacement. What is the probability all three are orange?

Accepted Answer

1/12

Answer

P = (5/10)(4/9)(3/8) = 60/720 = 1/12.

Question 5

In a school of 600 students, 360 take math and 240 take science. If 120 take both, what is the probability a randomly selected student takes exactly one of these subjects?

Accepted Answer

3/5

Answer

Exactly one = (360 − 120) + (240 − 120) = 240 + 120 = 360; P = 360/600 = 3/5.

Bluebook SAT Practice Test

Bluebook SAT Practice Test

Bluebook SAT Test Probability and Conditional Probability 11