If 20 parallal lines in a plane are intersected by another family of 20 parallal straight lines then find out the number of parallelograms formed????????
Now suppose your answer is n then find out the value of possitive square root of n
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if observe there will be 19 divisions in the parallelogram therefore number of parallelograms formed
={n(n+1)/2}^2 ----------- [n=no. of divisions]
={19(19+1)/2}^2
={19(20)/2}^2
={190}^2
(+)sqrt= 190
the parallel lines in one column cross to produce 1 9 × ( 1 × 1 ) , 1 8 × ( 2 × 1 ) , 1 7 × ( 3 × 1 ) , e t c which equals ∑ i = 1 1 9 i in each column therefore there are ( ∑ i = 1 1 9 i ) 2 parallelograms so n is ∑ i = 1 1 9 i which is ± 1 9 0 . the question asks for the positive square root so the answer is 1 9 0
Waw brett nice but i solved by using combinatorics
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how to solve using cimbinatroics?
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20C2=190 Hence 190 is the square root of n