9. The ages of Jo, her daughter and her grandson are all even numbers. The product of their three ages is 2024 . How old is Jo?
A 42
B 44
C 46
D 48
E 50
Solution
C

Let Jo have the age of $2 j$, her daughter's age be $2 d$ and her grandson's age be $2 g$. The product of their ages is $(2 g) \times(2 d) \times(2 j)$. We compare this with the prime factorisation of $2024=2 \times(2 \times 11) \times(2 \times 23)$.
So Jo is 46 .