Are Scissors Required? (Count 'em All 4!)

Count the total number of squares in the 5 × 6 5\times6 grid above.


This is one part of Quadrilatorics .


The answer is 70.

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2 solutions

Kenneth Tan
Mar 13, 2016

First count the number of 1 × 1 1\times1 squares, there are 5 × 6 = 30 5\times6=30 of them.

Now count the number of 2 × 2 2\times2 squares, there are 4 × 5 = 20 4\times5=20 of them.

Moving on to 3 × 3 3\times3 squares, there are 3 × 4 = 12 3\times4=12 of them.

Similarly there are 2 × 3 = 6 2\times3=6 4 by 4 squares and 1 × 2 = 2 1\times2=2 5 by 5 squares.

So the total number of squares in the grid is 30 + 20 + 12 + 6 + 2 = 70 30+20+12+6+2=70 .

Moderator note:

For the generalized version, see this note

Can you give solution using PnC

Abhishek Sharma - 5 years, 3 months ago

I solved it the same way

Ashish Menon - 5 years, 2 months ago
Zarin Tasnim
Mar 16, 2016

For the more visual learners

Btw the 1 at the top is just the 1 carried over for adding (not 1 more square)

Zarin Tasnim - 5 years, 3 months ago

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