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  1. If nPr= 720 nCr than the value r is ?
    1. 6
    2. 5
    3. 4
    4. 7
Correct Option: A

We know that, nPr = nCrr!
∵ nPr = 720nCr
⇒ nCr.r! = 720nCr
⇒ r! = 720
∴ r = 6


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