"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?

Since the difference in ages is odd, one of the digits must be odd and the other even. Of course the only even prime is 2. Once you've got that, the rest pretty much solves itself: 45 taken off an age ending in 2 must end in 7, so the odd prime is 7 and the ages are 72 and 27.

Posted by Jenny Turner on 2004-06-02 17:41:39