Probability Flashcards

A fair coin is tossed twice. What is the probability of getting two heads?

Answer: 1/4

P(HH) = P(H) × P(H) = 1/2 × 1/2 = 1/4 since the tosses are independent.

A standard die is rolled once. What is the probability of rolling a number greater than 4?

Answer: 1/3

Numbers greater than 4 are 5 and 6, so probability = 2/6 = 1/3.

In a class of 30 students, 12 play sports. If one student is chosen at random, what is the probability they do NOT play sports?

Answer: 3/5

Students not playing sports = 30 - 12 = 18; P = 18/30 = 3/5.

What is the probability of drawing an ace from a standard 52-card deck?

Answer: 1/13

There are 4 aces in 52 cards, so P = 4/52 = 1/13.

Two events A and B are mutually exclusive. P(A) = 0.3 and P(B) = 0.4. What is P(A or B)?

Answer: 0.7

For mutually exclusive events, P(A or B) = P(A) + P(B) = 0.3 + 0.4 = 0.7.

How many ways can 3 books be arranged on a shelf from a collection of 5 books?

Answer: 60

This is a permutation: P(5,3) = 5 × 4 × 3 = 60.