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प्रश्न
Ten points are marked on a straight line and 11 points are marked on another straight line. How many triangles can be constructed with vertices from among the above points
पर्याय
495
550
1045
2475
MCQ
उत्तर
1045
Explanation:
Triangle is formed by picking 3 points 2 from 1st line and 1 from 2nd or 1 point from 1st line or 2 from 2nd i.e.
⇒ `""^10C_2 xx ""^11C_1 + ""^10C_1 + ""^11C_2`
`= (10!)/(2!8!) xx (11!)/(1!10!) + (10!)/(1!9!) xx (11!)/(2!9!)`
⇒ 45 × 11 + 10 × 55
= 495 + 550 = 1045
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Permutation and Combination (Entrance Exam)
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