Folded A4

'Folded A4' printed from https://nrich.maths.org/

A sheet of A4 size paper (297mm x 210mm) is folded once and then laid flat on the table.

Which of these shapes could not be made?

a) b)

c) d)

e)

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.