Ex 6.4, 1 - Chapter 6 Class 11 Permutations and Combinations

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Ex 6.4, 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 Putting n = 10 10C2 = 10!/2!(10 − 2)! = 𝟏𝟎!/(𝟐! 𝟖!) = (10 × 9 × 8!)/((2 × 1)× 8!) = (10 × 9)/2 = 45

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Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo