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If ""^(8)P(r)=""^(8)P(r+1) then r is...

If `""^(8)P_(r)=""^(8)P_(r+1)` then r is

A

8

B

6

C

5

D

7

Text Solution

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The correct Answer is:
D
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Knowledge Check

  • If ""^(n)P_(5)+5.""^(n)P_(4)=""^(10)P_(r) then 'r' is

    A
    5
    B
    4
    C
    3
    D
    7

  • IF ""^(20)P_(r):""^(20)P_(r-1)=15 :1 then r=

    A
    10
    B
    14
    C
    6
    D
    8

  • If ""^(n)P_(r)=""^(n)P_((r+1)) and ""^(n)C_(r) = ""^(n)C_(r-1), then (n,r) =

    A
    `8,9`
    B
    `6,7`
    C
    `4,5`
    D
    `3,2`

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