f5math question?

wai1994926

2011-06-09 6:00 am

A coach wants to divide 12 athletes into three groups of 3,4 and 5.Find number of way of forming the groups.

回答 (2)

[匿名]

2011-06-09 6:32 am

✔ 最佳答案

Actually, there are a few ways to calculate the answer.

number of ways=

12C3 x (12-3)C4 x (12-3-4)C(12-3-4)=12C3 x 9C4 x 5C5 = 27720
12C4 x (12-4)C5 x (12-4-5)C(12-4-5)=12C4 x 8C5 x 3C3 = 27720
12C5 x (12-5)C4 x (12-5-4)C(12-5-4)=12C5 x 7C4 x 3C3 = 27720

Hope this can help you~ ^^

2011-06-08 22:38:04 補充：
in 12 athletes , we can firstly select (3/4/5) athletes. Then, there are (9/8/7) athletes left. This time, we select (4/5/4) athletes from (9/8/7) athletes. For the remainding athletes, we don't have choices but 1 choice only, so 5C5 or 3C3 is 1.

參考: math TB + me

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[匿名]

2011-06-09 7:18 pm

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