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प्रश्न
Answer the following:
Four parallel lines intersect another set of five parallel lines. Find the number of distinct parallelograms formed
उत्तर
To form a parallelogram, we have to select any 2 of 4 parallel lines and any 2 of another 5 parallel lines for intersecting.
∴ the number of parallelograms which can be formed
= 4C2 × 5C2
= `(4!)/(2!2!) xx (5!)/(2!3!)`
= `(4 xx 3)/(2 xx 1) xx (5 xx 4)/(2 xx 1)`
= 6 × 10
= 60.
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