Curious Incident
Evening Standard

A dazzling and pulse-pounding drama

Time Out New York

The Missing Square Puzzle

Christopher loves maths puzzles and explaining the unexplainable.

Missing Square Puzzle


The missing square puzzle has been confusing many minds, but not Christopher’s! We asked you all on social media if you can figure out where the missing square is coming from. If you couldn’t solve the conundrum, have no fear! Read on to discover where the extra square miraculously appears from…

The Answer: It’s an optical illusion. No, you’re not imagining that the square is appearing, but the 2 triangles are not actually identical.

The Explanation: The hypotenuse (the longest side of the triangle) is not actually straight. Although to the human eye both shapes seem like triangles, they are not actually true triangles, having a slight bend in this longer side. This bend is caused by the red and blue triangles hypotenuse having slightly different angles, making the combined hypotenuse have a slight bend. The difference, when spread over the whole length of the triangle, equates to the size of 1 grid square, which is where that empty gap comes from.

Phew, we’ll definitely sleep better tonight having that problem solved!

Check out more from our blog here.

More from the National Theatre