Permutation and combinations

Asked by  | 20th Mar, 2009, 10:25: AM

Expert Answer:

to make a parallelogram, we need to select two of the horizontal lines and two of the transvesals.

So,

 required number is

C(p,2) * C(5,2)

Answered by  | 20th Mar, 2009, 12:22: PM

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