One of our drinking companions in The Jolly Quizmaster was telling us about his two nephews, and the annual gift that he gives them.
Apparently the amount that he gives to them increases every year, and this year he is giving them 50% more than he gave them five years ago. We must have looked puzzled when he told us this, and so he went on to explain his method of working out what to give them.
Each year he takes the square of each nephews' age in whole years, and then find the difference between the two squares. He then gives both nephews that number of pounds.
"Very generous", we said, "and how old are the two boys?"
We were told that the elder is now 19 - how old is the younger?
The younger nephew is eleven.
The difference in the squares now is 361 - 121, so £240. Five years ago it was 196 - 36, so £160 - an increase of 50%.