Two friends, Alex and Bob, go to a bookshop, together with their sons Peter and Tim. All four of them buy some books. Each book costs a whole amount of shillings.

When they leave the shop, they notice that both fathers have spent 21 shillings more than their respective sons. Moreover, each of them paid per book the same amount of shillings as the number of books that he bought.

The difference between the number of books that Alex bought and that Peter bought is five.

Who is the father of Tim?

Peter buys n books for n^2 shillings.
Alex buys (n+5) books for (n+5)^2 shillings
If Alex is Peters father then
(n+5)^2 =n^2+21 for some n
cancelling gives
n=-4/10
Clearly Alex is not Peters father and is therefore Tims

Posted by Lee on 2003-09-15 02:44:35