Copyright © University of Cambridge. All rights reserved.

I am standing behind five pupils who are signalling a five-digit number to someone on the opposite side of the playground. From where I am standing the number looks like 23456. What number is actually being signalled?

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.**View the archive of all weekly problems grouped by curriculum topic*

View the current weekly problem