InterviewSolution
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In how many ways can 6 boys and 5 girls be arranged for a group photograph if the girls are to sit on chairs in a row and the boys are to stand in a row behind them? |
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Answer» Given : Number of boys = 6 and number of girls = 5 To find : Possible number of arrangements in a group photograph Let boys be b1, b2, b3, b4, b5, b6 and girls be g1, g2, g3, g4, g5 Possible arrangements are : b1 b2 b3 b5 b6 b4 g2 g4 g1 g5 g3 b2 b1 b5 b3 b4 b6 g2 g4 g5 g1 g3 In this arrangement, We are arranging boys and girls separately. Formula used : Number of arrangements of n things taken all at a point = P(n, n) P(n, r) = \(\frac{n!}{(n-r)!}\) ∴ Number of ways to arrange boys, = the number of arrangements of 6 things taken all at a time = P(6, 6) = \(\frac{6!}{(6-6)!}\) = \(\frac{6!}{0!}\) {∵ 0! = 1} = 6! = 6 × 5 × 4 × 3 × 2 × 1 = 720 Formula used : Number of arrangements of n things taken all at a point = P(n, n) P(n, r) = \(\frac{n!}{(n-r)!}\) ∴ Number of ways to arrange girls, = the number of arrangements of 5 things taken all at a time. = P(5, 5) = \(\frac{5!}{(5-5)!}\) = \(\frac{5!}{0!}\) {∵ 0! = 1} = 5! = 5 × 4 × 3 × 2 × 1 = 120 Now, We will get total number of ways by multiplying their separate arrangements ∴ Total number of ways = 720 × 120 = 86400 Hence, Possible number of arrangements in which 6 boys and 5 girls can be arranged for a group photograph with provided conditions are 86400. |
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