OlympiadMediumCombinatorics7–9
How many rectangles of all sizes can be found in a 4 \times 4 grid of unit squares? Sides must follow the grid lines.
Quantos retângulos de todos os tamanhos se podem encontrar numa grelha 4 \times 4 de quadrados unitários? Os lados têm de seguir as linhas da grelha.
Answer options
Solution
Step 1 of 3
- 1.A rectangle is fixed by choosing two of the 5 vertical lines and two of the 5 horizontal lines — that pairing is a bijection.