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Find r if (i) ""^5Pr=2^6P(r-1) (ii) "...

Find `r` if
(i) `""^5P_r=2^6P_(r-1)`
(ii) `""^5P_r=^6P_(r-1)`

Text Solution

Verified by Experts

(i) Given `""^5P_r=2^6P_(r-1)`
`=> (5!)/((5-r)!)=2*(6!)/((7-r)!)`
`=((7-r)!)/((5-r)!)=2*(6!)/(5!)`
`=(7-r)(6-r)=2xx6`
...
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Knowledge Check

  • Find r , if ""^(5) P_(r) =""^(6) P_(r-1) .

    A
    4
    B
    6
    C
    6
    D
    30

  • Find r, if ""^(5) P_(r) = 2 ""^(6) P_(r-1) .

    A
    3
    B
    4
    C
    5
    D
    6