Permutation & Combination
2011-04-28 2:14 am
A bag contains n balls with different color. Find the no. of way to draw r balls (r < n)from the bag (a) one by one (b) all r balls at a time if replacement is allowed.
回答 (3)
2011-04-28 5:09 am
✔ 最佳答案
(a) C(n,r)(b) n^r
Hope it helps
2011-04-28 5:26 am
Do you mean that
(a) one by one if replacement is allowed
(b) all r balls at a time
Then
a) Ans: n^r (order is important and in each of the r draws, there is n possibilities)
b) Ans: nCr (order is not important when choosing r balls from n balls at one time)
(a) one by one if replacement is allowed
(b) all r balls at a time
Then
a) Ans: n^r (order is important and in each of the r draws, there is n possibilities)
b) Ans: nCr (order is not important when choosing r balls from n balls at one time)
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