perplexus.info :: Just Math : Squares and Rectangles

Squares and Rectangles (Posted on 2004-01-21)

There is a grid of 20 squares by 10 squares. How many different rectangles are possible?
(Note that square is a rectangle).

See The Solution Submitted by Ravi Raja

Rating: 2.0000 (5 votes)

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solution

| Comment 9 of 22 |

The number of combos of 2 lines out of N lines is N(N-1)/2. The number of vertical combos times the number of horizontal combos is the total number of rectangles. Therefore 20*19*10*9/2=17100

After reading the other solutions I see I'm incorrect. The wording tripped me up.
Edited on January 21, 2004, 3:51 pm

Posted by Dan Porter on 2004-01-21 15:47:31

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