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The number of permutations of n objects, where p of them are of the same kind and the rest are all different, is given by which expression?
An! times p!
Bn! over p!
Cp! over n!
Dn! plus p!
Answer & Solution
Correct answer: B. n! over p!
1. Arranging all n objects as if distinct would give n factorial orders.
2. The p identical objects can be swapped among themselves in p factorial ways without changing the arrangement.
3. Dividing out that overcount gives n factorial over p factorial.
_Source: NCERT Class 11 Mathematics, Ch 6 'Permutations and Combinations'_
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