### Trice

ABCDEFGH is a 3 by 3 by 3 cube. Point P is 1/3 along AB (that is AP : PB = 1 : 2), point Q is 1/3 along GH and point R is 1/3 along ED. What is the area of the triangle PQR?

### Nine Colours

Can you use small coloured cubes to make a 3 by 3 by 3 cube so that each face of the bigger cube contains one of each colour?

### Marbles in a Box

How many winning lines can you make in a three-dimensional version of noughts and crosses?

# Pyramidal N-gon

##### Age 11 to 14 Short Challenge Level:

The base of a pyramid has $n$ edges. In terms of $n$, what is the difference between the number of edges of the pyramid and the number of faces?

If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.

This problem is taken from the UKMT Mathematical Challenges.
You can find more short problems, arranged by curriculum topic, in our short problems collection.