I just encountered this question. Here's my answer:
Given:
3 kids
product of their ages is 72.
Youngest child.
The youngest child means that all three kids have different ages.
We need to factor 72. Let us use prime factorization.
72 ÷ 2 = 36
36 ÷ 2 = 18
18 ÷ 2 = 9
9 ÷ 3 = 3
3 ÷ 3 = 1
1 x 2 x 2 x 2 x 3 x 3 = 72
Based on the factors we can assume the following ages:
2 x 4 x 9 = 72
3 x 4 x 6 = 72
1 x 8 x 9 = 72 I prefer this age combination.
1 x 3 x 24 = 72
1 x 4 x 18 = 72