The local pet store held a contest in which they drew ten children’s names as semifinalists.?

they drew ten children’s names as semifinalists. They then held another drawing from among those ten to determine who would win the top two prizes: a pair of homing pigeons or a cocktail. The ages of the semifinalists were 4, 5, 6, 7, 9, 10, 11, 13, 15, and 16. When the two winners’ names were drawn, the older winner was a teenager. What is the probability that the younger winner’s age was prime?

I count 24 combinations where at least one of the picks is a teenager.

For the 7 possibilites where the older child is 13, there are 3 with age equal to a prime number (5, 7, 11)

For the 8 possibilities where the older child is 15, there are 4 with age equal to a prime number (5, 7, 11, 13)

For the 9 possibilities where the older child is 16, there are 4 with age equal to a prime number (5, 7, 11, 13)

So, 24 possibilities in all, for which 11 have the younger child with age equal to a prime number. The odds: 11/24

Children of Poi Pet

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