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Ex 7.4, 1 - Chapter 7 Class 11 Permutations and Combinations (Term 2)

Last updated at March 22, 2023 by

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Ex 7.4, 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 βˆ’ 2)! = 𝟏𝟎!/(𝟐! πŸ–!) = (10 Γ— 9 Γ— 8!)/((2 Γ— 1)Γ— 8!) = (10 Γ— 9)/2 = 45

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