Related Collections

You may also like

problem icon

Grouping Goodies

Pat counts her sweets in different groups and both times she has some left over. How many sweets could she have had?

problem icon

What Number

I am less than 25. My ones digit is twice my tens digit. My digits add up to an even number.

problem icon

Odd Tic Tac

An odd version of tic tac toe

More Numbers in the Ring

Stage: 1 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Vidhya from Kensri School in India sent in a very well reasoned solution:

When we subtract an even number from an odd number, or vice versa, the difference is always odd. So if we fill up odd numbers and even numbers alternately, if there are an even number of squares, the differences will all be odd. But there is no solution (in other words the differences cannot all be odd) if there is an odd number of squares.




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. More information on many of our other activities can be found here.
Copyright © 1997 - 2012. University of Cambridge. All rights reserved.
NRICH is part of the family of activities in the Millennium Mathematics Project.