(C) The formula for permutation is $_{n}P_r = \frac{n!}{(n-r)!}$.Given $_{12}P_r = 1320$.We know that $_{12}P_r = 12 \times 11 \times 10 \times \dots

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(C) The formula for permutation is $_{n}P_r = \frac{n!}{(n-r)!}$.Given $_{12}P_r = 1320$.We know that $_{12}P_r = 12 \times 11 \times 10 \times \dots \times (12-r+1)$.Let us calculate the product of consecutive integers starting from $12$:$12 \times 11 = 132$$12 \times 11 \times 10 = 1320$Since the product of $3$ terms is $1320$,we have $r = 3$.

Class 11 Mathematics Permutation and Combination Definition of permutation, Number of permutations with or without repetition, Conditional permutations

Easy

If $_{12}P_r = 1320$,then $r = ..........$

A
$5$
B
$4$
C
$3$
D
$2$

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Permutation and Combination

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Definition of permutation, Number of permutations with or without repetition, Conditional permutations

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If $_{12}P_r = 1320$,then $r = ..........$

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The number of ways in which the letters of the word $ARRANGE$ can be permuted such that the $R$'s occur together is:

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