what is the probability?

Question

a standard 52 deck of cards are placed in a container. What is the probability that a card randomly selected from the container is a black card or 4?

a) 1/2

b) 7/13

c) 8/13

d) 15/26

Answer 1

Probability of (A or B) = Prob of A + Prob of B

Say A = the card is black

B = the card is a 4

So, Prob(A) = 1/2, since half of the cards are black and half are red

Prob(B) = 4/52 = 1/13, since there are four 4's in the deck.

Thus, Prob (A or B) = Prob(A) +Prob(B) = 1/2 + 1/13 = 15/26