A woman took her son to the fair and the first ride he went on was the merry-go-round. Whilst on the ride he came up with a clever puzzle with which to test his friends.

He realised that one third of everyone riding in front of him added to three quarters of all those riding behind him gave the total number of people on the ride, including the boy himself.

The puzzle he set his friends was to see if any of them were clever enough to work out how many people, in total, were riding on the merry-go-round. Can you work it out? We like this one because it’s quick yet clever little puzzle and makes a good coffee time challenge.

The solution: If the boy was able to calculate one third of all the people in front of him then the number must be divisible by 3. Likewise three quarters of the people behind him means that this number must be divisible by 4.

As the boy is on a merry-go-round the number of people in front of him is the same as the people behind him. The first number divisible by both 3 and 4 is 12. Three quarters of 12 is 9 and one third is 4. 9 + 4 = 13, the total number of people on the ride including the boy.