Maths Probabilities

2007-02-18 8:03 pm

CE(II)92
Two cards are drawn randomly from five cards A,B,C,D and E. Find the probability that card A is drawn while card C is not.

With steps and explanation please.
THANKS

回答 (2)

用戶110701

2007-02-18 8:38 pm

✔ 最佳答案

要係5張卡抽2張
就係5C2
你可以禁FX-3650
先禁SHIFT再禁÷
有10個可能性
要有A冇C係.....
AB、AD、AE
有這三個可能性
所以係3/10啦

2007-02-18 12:39:20 補充：
禁Calculator過程先禁5再禁SHIFT再禁÷再禁2再禁exe

參考: KING

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Sammy

2007-02-18 8:23 pm

To solve this problem, need to divide it in two parts. First, the first card drawn is A and the second card is not C. Secondly, the first card is not C but the 2nd card is A.

1. The first card drawn is A and the second card is not C.
First card is A : 1/5
Second card is not C, since only 4 cards left: 3/4
Therefore , the probability of the this option is: 1/5 x 3/4 = 3/20

2. The first card is not C but the 2nd card is A
First card is not C: 4/5
Second card is A: 1/4
Therefore , the probability of the this option is: 4/5 x 1/4 = 4/20

Add these two scenario together: 3/20 + 4/20 = 7/20 = 0.35

Overall, the answer is: 1/5 x 3/4 + 4/5 x 1/4 = 0.35

2007-02-18 22:50:45 補充：
I made a mistake in Step 2. It shall be:2. The first card is not C but the 2nd card is AFirst card is not C nor A, since A is not allowed to be drawn first: 3/5Add these two scenario together: 3/20 3/20 = 3/20 = 0.3Overall, the answer is: 1/5 x 3/4 3/5 x 1/4 = 0.3

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