mrwaxy wrote:

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

IMO A is the answer

here is the reasoning

let the total number of steros be x therefore we get 2x/3 (basic) and x/3 deluxe steros

lets assume that it takes y hours to produce one basic stero, accordingly it takes 7y/5 hours to produce one deluxe stereo.

Combining both together we get the following

hours to produce 2x/3 basic stereos = 2xy/3

and hours to produce x/3 deluxe stereos = 7xy/15

total hours =17xy/15

therefore we get

(7xy/15)/(17xy/15)

which derives to 7/17

HTH

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