We have two sets of parallel lines.
Assuming that the two sets are not parallel to each other, we can say that some parallelograms will be formed.
We need to determine the number of parallelograms.If we take any two lines from each of the set a parallelogram will be formed. Hoping that you know the concept of permutations and combination i would like to give the solution of it.
We have to select any two lines from each set.
From one set we can do it in 4C2 ways.
4C2=6From the other we can do it in 7C2 ways.
7C2=21As the work is not completed only by selecting, we have to multiply the above
resuls.i.e 4C2 x 7C2 = 6 x 21 = 126
-sam
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