You may also like

problem icon

Consecutive Numbers

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

problem icon

Roll These Dice

Roll two red dice and a green dice. Add the two numbers on the red dice and take away the number on the green. What are all the different possible answers?

problem icon

Domino Square

Use the 'double-3 down' dominoes to make a square so that each side has eight dots.

Sealed Solution

Age 7 to 11 Challenge Level:

A set of ten cards, each showing one of the digits from $0$ to $9$, is divided up between five envelopes so that there are two cards in each envelope. The sum of the two numbers inside it is written on each envelope:

five envelopes with the numbers 7, 8, 13, 14 and 3 written on them (one number per envelope)

What numbers could be inside the "8" envelope?

Thank you to Alan Parr for allowing us to adapt one of his problems.


The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to embed rich mathematical tasks into everyday classroom practice.
Copyright © 1997 - 2019. University of Cambridge. All rights reserved.
NRICH is part of the family of activities in the Millennium Mathematics Project.