Author: Henry Dudeney

Henry Ernest Dudeney (1857 – 1930) was an English author and mathematician who specialized in logic puzzles and mathematical games. He is known as one of the country's foremost creators of mathematical puzzles.

First, print and cut the pieces below. Then, arrange them so that they form a triangle and then rearrange them so that they form a square.

The solution is shown below.

What is fascinating about these dissections is that one can transform into the other by keeping the pieces attached to each other in a chain and simply rotating them around the hinge points.


Replace every letter with a different digit between 0 and 9, such that you get a correct calculation.

The answer is 9567 + 1085 = 10652.

You can first see that M = 1. Then S = 8 or 9 and O = 0. MORE is at most 1098, and if S = 8, then E = 9, N is either 9 or 0, but this is impossible. Therefore S = 9, N = E + 1. You can check easily the 6 possibilities for (N, E) and then find the answer.