You may also like

problem icon

Doodles

Draw a 'doodle' - a closed intersecting curve drawn without taking pencil from paper. What can you prove about the intersections?

problem icon

Russian Cubes

I want some cubes painted with three blue faces and three red faces. How many different cubes can be painted like that?

problem icon

Picture Story

Can you see how this picture illustrates the formula for the sum of the first six cube numbers?

Take Three from Five

Stage: 4 Challenge Level: Challenge Level:2 Challenge Level:2


Start with the problem What Numbers Can We Make?


Think of a simpler problem:
If you choose 2 from 3 numbers, you can always select 2 numbers that add up to an even number. Why?