JOMO 7, Short 1
Probability
Level
3
How many rectangles are there in a sized chess board?
The answer is 22050.
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1 solution
In a 20*14 chessboard, there are 21 horizontal lines and 15 vertical lines.To make a rectangle, we have to choose 2 lines out of 21 and then 2 lines out of 15. Hence there are (21 C 2)(15 C 2)= 22050 rectangles that can be formed.