Problem Solving

Company S produces two kinds of stereos: basic and deluxe. Of the stereoes produced by Company S, 2/3 were basic and the rest were deluxe. If it takes 7/5 as many hours to produce a delux stereo as it does a basic, the the number of hours it took to produce the delux 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

The no. of Basic stereos = 2/3, so deluxe=1-2/3 or 1/3
Let us assume it takes y hrs to produce a basic. so, it takes 7/5y hrs to produce a deluxe.

time taken to produce stereos = no. X time taken
So for basic = 2/3 X y
deluxe = 1/3 X 7/5y = 7/15y

Total time taken to produce stereos = Basic + deluxe = 2/3y + 7/15y = 17/15y

So, 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?

(7/15)y/(17/15)y or 7/17

Ans: A