Love of lines

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


The answer is 190.

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3 solutions

Rudresh Tomar
Nov 12, 2014

20C2=190 Hence 190 is the square root of n

Jenosha Sarah
Oct 3, 2014

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

Brett Hartley
Sep 1, 2014

the parallel lines in one column cross to produce 19 × ( 1 × 1 ) , 18 × ( 2 × 1 ) , 17 × ( 3 × 1 ) , e t c 19 \times (1 \times 1), 18 \times (2 \times 1), 17 \times (3 \times 1), etc which equals i = 1 19 i \sum_{i=1}^{19} i in each column therefore there are ( i = 1 19 i ) 2 (\sum_{i=1}^{19} i)^{2} parallelograms so n \sqrt{n} is i = 1 19 i \sum_{i=1}^{19} i which is ± 190 ±190 . the question asks for the positive square root so the answer is 190 \boxed{190}

Waw brett nice but i solved by using combinatorics

Aman Sharma - 6 years, 9 months ago

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how to solve using cimbinatroics?

aaron paul - 6 years, 9 months ago

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Ohhh sorry yar it was combinatorics :p

Aman Sharma - 6 years, 9 months ago

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