"I've always been 45 years older than your Dad", said Grandma to young grandson.

"But now the two digits in my age, both prime, are the reverse of the two in your Dad's age".

How old is Grandma?

72

The only prime digits are 2, 3, 5, and 7. If you add 45 to the number, you'd get both prime digits too, since the age is reversed. If you add 5 to any odd digits, you'd get an even one (except you'd get 0 in the case of 5, which would not make sense). So her age must end in a 2. If you add a 5 to it, you'd get 7. If there is an answer, it must be 72, which does work.

Posted by np_rt on 2003-02-28 08:37:24