実際の問題20
A daughter, a Mom, and a grandmother were asked about
their ages. Mom answered "our ages are prime numbers
in which i) the average of ANY TWO of the numbers is
a prime and ii) the average of all three of the numbers
is a prime." What were their ages?

11,29,61
11,47,71
7,29,71
13,37,79
none of the above
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娘、母、祖母がいて、年齢を聞いてみた。母の答えは、
「私たちの年齢は素数よ。しかも、どの2人の年齢の平均を
とっても素数になるし、3人の年齢の平均も素数だわ」
彼女らの年齢は？