Bluebook SAT Test Probability and Conditional Probability 7

Question 1

A jar contains 4 red, 3 blue, and 5 green marbles. One marble is drawn at random. What is the probability of drawing a red or blue marble?

Accepted Answer

7/12

Answer

Red + blue = 4 + 3 = 7 out of 12 total; P = 7/12.

Question 2

The two-way table shows 240 students by grade and lunch preference.

Hot Lunch  Packed Lunch
Grade 7              60            40
Grade 8              70            70

A Grade 8 student is selected at random. What is the probability the student prefers hot lunch?

Accepted Answer

1/2

Answer

Grade 8 total = 70 + 70 = 140; hot lunch = 70; P = 70/140 = 1/2.

Question 3

A fair coin and a fair die are both tossed. What is the probability of getting heads and an even number?

Accepted Answer

1/4

Answer

P(heads) = 1/2; P(even on die) = 3/6 = 1/2; independent, so P = (1/2)(1/2) = 1/4.

Question 4

A test has 50 questions: 20 multiple choice, 20 short answer, and 10 essay. If one question is picked at random, what is the probability it is NOT an essay question?

Accepted Answer

4/5

Answer

Non-essay = 20 + 20 = 40; P = 40/50 = 4/5.

Question 5

Events M and N are mutually exclusive with P(M) = 0.25 and P(N) = 0.40. What is P(M or N)?

Accepted Answer

0.65

Answer

For mutually exclusive events, P(M or N) = P(M) + P(N) = 0.25 + 0.40 = 0.65.

Bluebook SAT Practice Test

Bluebook SAT Practice Test

Bluebook SAT Test Probability and Conditional Probability 7