Copyright © University of Cambridge. All rights reserved.

'Grid Without Lines' printed from https://nrich.maths.org/

Show menu


At least one point must be removed from each of the three horizontal lines; so at least three points need to be removed.

Removing the three points lying on either diagonal does what is required.
 
 
This problem is taken from the UKMT Mathematical Challenges.
You can find more short problems, arranged by curriculum topic, in our short problems collection.