### Consecutive Numbers

An investigation involving adding and subtracting sets of consecutive numbers. Lots to find out, lots to explore.

### Calendar Capers

Choose any three by three square of dates on a calendar page...

### Building Tetrahedra

Can you make a tetrahedron whose faces all have the same perimeter?

# 11x11 Square

##### Age 11 to 16 Challenge Level:

There's an interesting trick you can do with an $11 \times 11$ square...

It's possible to make five rectangles, each with different widths and lengths, using each of the following dimensions once only: $1, 2, 3, 4, 5, 6, 7, 8, 9, 10$, that can be used to tile the $11 \times 11$ square!

Convince yourself that only one of the arrangements below could satisfy these conditions.

Can you find two different solutions (not just reflections or rotations)?

With thanks to Don Steward, whose ideas formed the basis of this problem.