Question

Every cereal box has a gift inside, but you cannot tell from the outside what the gift is. The store manager assures you that 15 of the 50 boxes on the shelf have the secret decoder ring. The other 35 boxes on the shelf have a different gift inside. If you randomly select two boxes of cereal from the shelf to purchase, what is the probability that BOTH of them have the secret decoder ring?

Answer 1

3/35.

Explanation:

Probability (the first one selected has the decoder ring) = 15/50 = 3/10.

Probability (the second one selected has the decoder ring) = 14/49 = 2/7.

Therefore the probability that both have the ring =

3/10 * 2/7

= 6/70

= 3/35.

Note: The probabilities are multiplied because the 2 events are independent.

Answer 2

3/35

Explanation:

(15/50)×(14/49)

= 3/35 or 0.0857