1. There are 25 boys and 12 girls in class 5C. Among these students 16% of the boys and 75% of the girls have pets. If two students are chosen at random from that class, find the probability of each of the following events.
(a) Both of the two students do not have pets.
(b) Only one of the students has pets.
The answer are (a) 0.414 and (b) 0.468 respectively.
※請列明清楚計算步驟※
關於Probability的簡單Maths.問題
2009-10-10 7:21 am
回答 (1)
2009-10-10 7:31 am
✔ 最佳答案
a)25*16% = 4 boys have pets12 * 75% = 9 girls have pets
total 9 + 4 = 13 students have pets.
P(Both of the two students do not have pets.)
= (25+12 - 13)/37 * (25+11 - 13)/36
= 552/1332
= 0.414...
(b) P( Only one of the students has pets.)
= 1 - P(All have pets) - P(All have not pets)
= 1 - (13/37)(12/36) - 552/1332
= 1 - 156/1332 - 552/1332
= 0.468...
收錄日期: 2021-04-21 22:05:12
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20091009000051KK01665