### 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?

In a $7$-digit numerical code each group of four adjacent digits adds to $16$ and each group of five adjacent digits adds to $19$. What is the sum of all seven digits?