弱问一道GWD题

zccwen

On a certain transatlantic crossing, 20 percent of a ship’s passengers held round-trip tickets and also took their cars abroad the ship.  If 60 percent of the passengers with round-trip tickets did not take their cars abroad the ship, what percent of the ship’s passengers held round-trip tickets?

 

A.      33 1/3%

B.       40%

C.      50%

D.      60%

E.       66 2/3%

Answer:  E

 请问很容易知道整船人20％又RT票和车，40％的RT票乘客有车。后面怎么得出50％？难道是相除吗？ 谢谢

k_wang_2008

答案应该是C.

确实就是相除.概率论里应该有个基本定理,P(A交B)=P(A)*P(A|B).这道题里P(A交B)=20%,P(A|B)=40%,求P(A).

zccwen

Many thanks!!!

prettycoolne

I think that the word "abroad" may be replaced by the word "aboard", because i can't understand what the meaning of "took the car abroad the ship"....Is my opinion wright? 

[此贴子已经被作者于2009-7-9 3:24:35编辑过]

zhaozihan

同问