Question

12 points if someone gets it right.

You randomly draw twice from this deck of cards. What is the probability of drawing a 7, then drawing a prime number, replacing the first card? write you answer as a fraction.

Numbers: 7 6 4 9 4 7 9

Answer 1

4/49

Explanation:

7, 6, 4, 9, 4, 7, 9

total number of cards: 7

number of 7's: 2

First drawing:

p(7) = 2/7

Replace the 7.

total number of cards: 7

number of prime numbers: 2 (only the 7's are prime numbers)

p(7) = 2/7

The events are independent, so the overall probability is the product of the individual probabilities.

p(7 then prime) = 2/7 × 2/7 = 4/49