Question

Please help me to do this sum(marked one)..... correct one marked as brainlist...

Answer 1

nPr = 504

=> n!/(n - r)! = 504 ...............= >(1)

again, nCr = 84

=> n!/r!(n - r)! = 84 .............. => (2)

Now from (1/2) we have,

r! = 504/84

=> r! = 6 = 3.2.1 = 3!

=> r = 3

Now putting r = 3 in (1) we have,

n!/(n - 3)! = 504

=> n(n - 1)(n - 2)(n - 3)!/(n - 3)! = 504

=>n(n - 1)(n - 2) = 9.8.7

=> n = 9

Hence , n = 9 and r = 3

Hope this helps you

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Answer 2

Step-by-step explanation:

nPr = 504

=> n!/(n - r)! = 504 ..............(1)

again, nCr = 84

=> n!/r!(n - r)! = 84 .............. (2)

Now from (1/2) we have,

r! = 504/84

=> r! = 6 = 3.2.1 = 3!

=> r = 3

Now putting r = 3 in (1) we have,

n!/(n - 3)! = 504

=> n(n - 1)(n - 2)(n - 3)!/(n - 3)! = 504

=>n(n - 1)(n - 2) = 9.8.7

=> n = 9

Hence , n = 9 and r = 3 (ANSWER)

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