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Question
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?
Solution
Number of arrangements of the boys = Number of arrangements of the 6 boys taken 6 at a time = 6!
Number of arrangements of the girls = Number of arrangements of the 5 girls taken 5 at a time = 5!
Total number of arrangements = 6! x 5! = 86400
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