Ex 7.4, 1 - If nC8 = nC2, find nC2 - Chapter 7 Class 11 - Ex 7.4

  1. Chapter 7 Class 11 Permutations and Combinations
  2. Serial order wise
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Ex7.4, 1 If nC8 = nC2, find nC2 . Given nC8 = nC2 If nCr = nCp then either r = p or r = n – p Thus, nC8 = nC2 8 = n – 2 8 + 2 = n 10 = n n = 10 Calculating nC2 Put n = 10 10C2 = 10!/2!(10 − 2)! = 10!/2!(10 − 2)! = 10!/(2! 8!) = (10 × 9 × 8!)/((2 × 1)× 8!) = (10 × 9)/2 = 45

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