permutation and combination

Asked by  | 20th Mar, 2009, 08:09: PM

Expert Answer:

15Pr : 16Pr =3:4

15!/(15-r)! :16!/(16-r)! = 3:4

15!(16-r)!/(15-r)!16! =3/4

(16-r)/16 =3/4

So r = 4

Answered by  | 20th Mar, 2009, 08:19: PM

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