Probability & Statistics Question?
2020-01-30 6:27 am
A school club consists of 20 male and 5 female students. In how many ways can two male and two female students be chosen?
回答 (2)
2020-01-30 6:36 am
✔ 最佳答案
Hint:combinatorics
---> 1900 ways
2020-01-30 8:52 am
20C2 * 5C2 =>
(20! / (2! * (20 - 2)!)) * (5! / (2! * (5 - 2)!)) =>
20! * 5! / (2! * 18! * 2! * 3!) =>
20 * 19 * 18! * 5 * 4 * 3! / (2 * 2 * 18! * 3!) =>
20 * 19 * 5 * 4 / 4 =>
20 * 19 * 5 =>
100 * 19 =>
1900
(20! / (2! * (20 - 2)!)) * (5! / (2! * (5 - 2)!)) =>
20! * 5! / (2! * 18! * 2! * 3!) =>
20 * 19 * 18! * 5 * 4 * 3! / (2 * 2 * 18! * 3!) =>
20 * 19 * 5 * 4 / 4 =>
20 * 19 * 5 =>
100 * 19 =>
1900
收錄日期: 2021-04-24 07:43:45
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https://hk.answers.yahoo.com/question/index?qid=20200129222729AAsnMqb