Ages 5-7: Jigsaw
First make a six by four grid.
1. Make eight pieces like this:
3. Now make six pieces like this:
2. Fit them all on the grid without making this shape:
4. Fit them all on the grid without making this shape:
Age 9-11: Count the triangles How many triangles can you see in the square?
Brainteaser solutions from page 54
Count the triangles
There are 44 triangles altogether - 10 in each quadrant, and the four largest, each equal in area to half of the square, are formed by the two diagonals of the square.