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mathQ(probability)
發問:
In a swimming pool,70% of the swimmers are male. It is known that 20% of the male swimmers and 60% of the female swimmers wear swimming caps. Given that two swimmers wear swimming caps,find the probability that one of them is a male swimmer. Given your answer correct to decimal places.Ans=0.49我唔識計,請教教我 顯示更多 In a swimming pool,70% of the swimmers are male. It is known that 20% of the male swimmers and 60% of the female swimmers wear swimming caps. Given that two swimmers wear swimming caps,find the probability that one of them is a male swimmer. Given your answer correct to decimal places. Ans=0.49 我唔識計,請教教我
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First of all, let's consider the tree-diagram. 圖片參考：http://i726.photobucket.com/albums/ww265/physicsworld2010/physicsworld01Mar231331.jpg?t=1237786357 P(a swimmer wears swimming cap) = (0.7)(0.2) + (0.3)(0.6) = 0.32 P(two swimmers wear swimming caps) = (0.32)2 = 0.1024 The required probability = P(one is male and one is female│two wearing caps) = P(one male and one female wearing caps) / P(two swimmers wear caps) = [2 X (0.7)(0.2) X (0.3)(0.6)] / 0.1024 = 0.49 (cor. to 2 d.p.)
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