If m parallel lines in plane are intersected by a family of n parallel lines. Find the number of parallelograms formed.
None of these
A parallelogram is formed by choosing two straight lines from the set of mparallel lines and two straight lines from the set of n parallel lines.
Two straight lines from the set of m parallel lines can be chosen in mC2ways and two straight lines from the set of n parallel lines can be chosen innC2 ways. Hence, the number of parallelograms formed.
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