Imagine a grid comprising 20 X 20 squares.
How many squares, of any size, in total?
A box for your workings out:
Hint: How many 1x1 squares are there, how many 2x2?
There is one 20x20, four 19x19, nine 18x18, sixteen 17x17, etc. The sum of the counts is 1 + 4 + 9 + 16 + 25 + 36 + ... + 400 = 2870.
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