Consider a 5×5 grid of equal unit squares. If one corner unit square is removed, how many squares of all sizes can still be formed? Choose the correct answer.

Step-by-step solution

1. Total squares in a full 5×5 grid: $displaystyle{1}^2+2^2+3^2+4^2+5^2=55$.
2. Identify squares that involve the removed corner: for each size $k$ ($1lekle5$) there is exactly one $k\times k$ square whose top‑left corner is at the removed unit, so 5 squares are lost.
3. Subtract the lost squares: $55-5=50$.
4. Therefore 50 squares can still be formed.

Concept tested: Counting squares after removing a corner

Published 1 October 2026 · How this solution was prepared and checked