Solved Example #5

Saturday, February 9th, 2013


Question : Find the probability that a rectangle selected at random from a 10*10 square is a square?

a.17/55

b.7/55

c.9/55

d.16/55

 

Answer : 

Total number of rectangles = 11C2 * 11C2 = 55*55

Total number of squares = 1^2 + 2^2 ……. 10^2 = 10*11*21/6 = 5*11*7 = 55*7

Required probability = 55*7 / 55*55 = 7/55

 

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