請問依條probability 題目入面... [10分]

2007-09-22 5:05 am

In a class of 30 students, there are 17 girls and 13 boys. Five are A students, and three of these students are girls. If a student is chosen at random, what is the probability of choosing a girl or an A student?

答案係19/30

請問choosing a girl同埋choosing an student 依兩件事
係咪independent 呢? (我已經知道佢地唔係mutually exclusive)
請做d數出黎證明下佢地係或者唔係independent
唔該晒.

更新1:

sorry 我意思係 choosing a girl 同埋 choosing an A student 依兩件事係咪independent

更新2:

唔係呀，我從學術ｏ既角度出發先想理解下佢地係咪independent

回答 (1)

2007-09-22 5:20 am

✔ 最佳答案

答案明顯地係17/30(女仔)+2/30(男仔係A)
至於你想話咩independent，我唔知你想講咩
不過題目話明係女仔***or****係A
係or 唔係 and.
如果係and 答案應該係3/30=1/10，因為佢要又係A又係女仔
至於original 既題目係女仔 or A，女仔既話姐係至少有17
由於or 唔駛理A個3個女仔，只係理仲有2個男仔，咁咪加埋搞點

2007-09-22 19:43:25 補充：
係independent既不過有3個女仔會係既girl又係A student姐p.s.你中幾ga，要問e d野既?識計就得啦，理咩independent

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