Class 11MathematicsPermutations and CombinationsDefinition of permutation, Number of permutations with or without repetition, Conditional permutations
EasyIf $^n{P_r} = 720 \times {^n{C_r}}$,then $r$ is equal to:
- A$6$
- B$5$
- C$4$
- D$7$
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