Copyright © University of Cambridge. All rights reserved.

'Sliding Coins' printed from http://nrich.maths.org/

Show menu

See all short problems arranged by curriculum topic in the short problems collection

The diagram shows 10 identical coins which fit exactly inside a wooden frame. As a result each coin is prevented from sliding. What is the largest number of coins that may be removed so that each remaining coin is still unable to slide?
10 coins inside wooden triangle

 

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.