Q. There is a set of $m$ parallel lines intersecting a set of another $n$ parallel lines in a plane. The number of parallelograms formed, is
A) $\ ^{m - 1}C_{2}.\ ^{n - 1}C_{2}$
B) $\ ^{m}C_{2}.\ ^{n}C_{2}$
C) $\ ^{m - 1}C_{2}.\ ^{n}C_{2}$
D) $\ ^{m}C_{2}.\ ^{n - 1}C_{2}$
Explanation
(b)
Since, a set of $m$ parallel lines intersecting a set of another $n$ parallel lines in a plane, then the number of parallelograms formed is $\ ^{m}C_{2} \times \ ^{n}C_{2}$.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.