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Permutation and Combination Problem

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by ganeshrkamath » Mon Sep 09, 2013 11:57 pm
sukhman wrote:In how many ways can 3 letters out of five distinct 5 distinct letters A, B, C, D and E be arranged in a straight line so that A and B never come together? Answer (5C3 - 3C1) × 3!
Total = 5P3
With A and B => 3C1 * 3! = 6

Total number of possible arrangements = 5P3 - 3C1 * 3! = 5C3 * 3! - 3C1 * 3!
= (5C3 - 3C1) * 3!

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