[問題] 機率問題
Three balls are to be randomly selected without replacement from an urn
containing 20 balls numbered 1 through 20. If we bet that at least one
of the drawn balls has a number as large as or larger than 17, what is the probability
that we win the bet?
我的算法:(4*3*2+4*3*16+4*16*15)/20*19*18
這樣算法錯在哪?
我知道可以用全沒中的方式算,但我想知道我錯在哪?
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07/17 13:50, , 1F
07/17 13:50, 1F
→
07/17 13:51, , 2F
07/17 13:51, 2F
→
07/17 13:51, , 3F
07/17 13:51, 3F
→
07/17 13:52, , 4F
07/17 13:52, 4F
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07/17 13:53, , 5F
07/17 13:53, 5F
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07/17 13:53, , 6F
07/17 13:53, 6F
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