Copyright © University of Cambridge. All rights reserved.

'Which Numbers? (1)' printed from http://nrich.maths.org/

Show menu


I am thinking of three sets of numbers less than $101$. They are the red set, the green set and the blue set.
Can you find all the numbers in the sets from these clues?

These numbers are some of the red set: $19, 37, 55, 73, 82$, but there are others too.
These numbers are some of the green set: $5, 30, 35, 50, 70,100$, but there are others too.
These numbers are some of the blue set: $18, 27, 54, 72, 81, 99$, but there are others too.

These numbers are in one of the sets: $9, 10, 15, 37, 36, 85$, but there are others too.
These numbers are in two of the sets: $45, 55, 90$.
These numbers are not in any of the sets: $4, 12, 26, 42, 56, 77, 97$, but there are others too.

There are nine numbers altogether in the red set, eleven numbers in the blue set and twenty numbers in the green set.

There are three numbers that are in two of the sets.
There are no numbers that are in all three sets.
There are $63$ numbers altogether that are not in any of the sets.

You can download a sheet of all this information that can be cut up into cards.

Can you find the rest of the numbers in the three sets?
Can you give a name to the sets you have found?