[問題]GWD27-9

[magic]

Q9:
Company S produces two kinds of stereos: basic and deluxe. Of the stereos produced by Company S last month, 2/3 were basic and the rest were deluxe. If it takes 7/5 as many hours to produce a deluxe stereo as it does to produce a basic stereo, then the number of hours it took to produce the deluxe stereos last month was what fraction of the total number of hours it took to produce all the stereos?

A.7/17
B.14/31
C.7/15
D.17/35
E.1/2

答案是A
請問要怎麼算壓??

[spreewell]

設製作basic stereo的時間為X，製作deluxe stereo的時間便為7/5X
又總量的2/3為basic stereo，另外1/3為deluxe stereo
所以比例為:
(1/3)(7/5)X / (2/3X) + (1/3)(7/5)X = 7/17

答案為A

[magic]

謝謝大大喔
了解嚕