Maths problem

This is one of the difficult problems that I've solved.

The five children in the Wipere family are Mihi, Sam, Rawiri, Tiere, Whitu. At Christmas, each child buys a $5 present fore each of the other children. How much is spent in total by all the children?

4x5=20

20x5=100

So there is only one child that is buying a Christmas present for all 4 of them. So he is spending 5$ each for each child. He won't buy a Christmas present for himself. That will equal to 20$, 20$ x 5 = 100$