A door-to-door salesman is trying to persuade a woman to buy his product. Eventually she says "I will buy one if you can answer this question. I have three daughters and you have not seen any of them. The product of their ages is 36 and the sum of their ages in the same as my house number. How old are they?"

The salesman immediately goes outside to find out the house number, and returns saying "It is not possible to find their ages from the information you have given me - I need something more."

She replies "You are correct, you do need more information - my eldest daughter plays the piano".

The salesman then tells her the daughters' ages and makes the sale.

What are their ages, and incidentally what is the house number?

We'll give the answer and explanation on Monday.