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manasi_sh: Senior | Next Rank: 100 Posts; Posts: 69; Joined: Sat Sep 15, 2007 1:54 am

by manasi_sh » Fri Oct 05, 2007 4:03 am

A certain quantity of 40% solution is replaced with 25% solution such that the new concentration is 35%. What is the fraction of the solution that was replaced?
(A) 1/4
(B) 1/3
(C) 1/2
(D) 2/3
(E) ¾

plz explain..

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Source: Beat The GMAT — Problem Solving | Fri Oct 05, 2007 4:03 am

kajcha: Master | Next Rank: 500 Posts; Posts: 321; Joined: Tue Aug 28, 2007 5:42 am; Thanked: 1 times

by kajcha » Fri Oct 05, 2007 4:10 am

suppose the original solution is x unit and y units are replaced

so, we can write

(x-y)*0.4 + 0.25*y = 0.35*x. Solve for

y/x = 1/3 ANS

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