Bluebook SAT Test Probability and Conditional Probability 6

Question 1

A class has 24 students. The probability of any student being absent on a given day is 0.05. What is the expected number of absent students?

Accepted Answer

1.2

Answer

E = n × p = 24 × 0.05 = 1.2.

Question 2

The two-way table shows 200 voters by party and stance on a bill.

Favor  Oppose
Democrat       70      30
Republican     20      80

Given that a voter favors the bill, what is the probability the voter is a Republican?

Accepted Answer

2/9

Answer

Total favoring = 70 + 20 = 90; Republicans favoring = 20; P = 20/90 = 2/9.

Question 3

Cards numbered 1 through 20 are shuffled. One card is drawn at random. What is the probability the card shows a multiple of 3 or a multiple of 5?

Accepted Answer

2/5

Answer

Multiples of 3: {3,6,9,12,15,18} = 6; multiples of 5: {5,10,15,20} = 4; overlap {15} = 1; union = 9; P = 9/20.

Question 4

A bag has 5 red and 5 blue chips. Two chips are drawn without replacement. What is the probability both are the same color?

Accepted Answer

4/9

Answer

P(RR) = (5/10)(4/9) = 20/90; P(BB) = (5/10)(4/9) = 20/90; total = 40/90 = 4/9.

Question 5

A company's hiring data shows: 40% of applicants pass the written test and, of those, 30% pass the interview. What percent of all applicants get hired?

Accepted Answer

12%

Answer

P(pass written and interview) = 0.40 × 0.30 = 0.12 = 12%.

Bluebook SAT Practice Test

Bluebook SAT Practice Test

Bluebook SAT Test Probability and Conditional Probability 6