Solution Y is 30 percent liquid X and 70 percent water. If 2 kilograms of water evaporate from 8 kilograms of solution Y and 2 kilograms of solution Y are added to the remaining 6 kilograms of liquid, what percent of this new solution is liquid X? (A) 30% (B) 33.33% (C) 37.5% (D) 40% (E) 50%

Soln Y Contains 30% X and 70% Water 8 Litres of water contains 30*8/100 = 2.4 Litres of soln x ....(1) and 8-2.4= 5.6 Litres of Water out of which two litres of water evaporate leaving 3.6 Litres of water...(2) Now 2 litres of Y are added to the above 6 litres of solution y. The breakup on these two litres is as follows: Litres of Solution X=30(2)/100=0.6 ....(3) Litres of Water=1.4 ....(4) From 1 and 3 the total amt of X in the final soln is 2.4+0.6= 3 From 2 and 4 The total volume of water is 3.6+1.4= 5 Total volume of mixture is 8. Hence percentage of soln x in the final mixture is (3/8) *100 = 37.5 Hence C However, this problem is best solved using weighted averages. (6/8)*(40)+(2/8)*(30)=37.5 Hence C

knight247 wrote:Soln Y Contains 30% X and 70% Water If 2 out of 8 litres evaporate then there are 6 litres left. Litres of Solution X =30(6)/100= 1.8....(1) Litres of Water=6-1.8= 4.2....(2) Now 2 litres of Y are added to the above 6 litres of solution y. The breakup on these two litres is as follows: Litres of Solution X=30(2)/100=0.6 ....(3) Litres of Water=1.4 ....(4) From 1 and 3 the total amt of X in the final soln is 1.8+0.6= 2.4 The total volume of the mixture is 8. So we have (2.4/8)*100=[spoiler]30%[/spoiler] Hence A However, this problem is best solved using weighted averages. (6/8)*(30)+(2/8)*(30)=30 Hence A Hi Knight247, Your approach is correct and I have also followed the same way. But the catch in the question is that 2kgs of WATER is evaporated not the 2kgs of Y solution. Check the question again. U shd be able to get the correct soln after correcting the error. Regards, Chetan

Only water evaporates. Amount of solution X is the same. Initial quantity of liquid X = 0.3*8 = 2.4 After water evaporates 2 litres of solution Y is added - Liquid X = 0.3 * 2 = 0.6 Total Liquid X = 3. Percentage = 3/8 * 100 = 37.5

In 8 kg of Y, X = .3 * 8 = 2.4 kg Water(W) = .7 * 8 =5.6 kg. Now if 2 kg of water is removed, Water left = 3.6 kg. and 2 kg of Y is added in which , X =.3 * 2 =.6 kg. then in 8 kg Y we have, Amount of X = 2.4 + .6 = 3 kg So, % of X =3/8 * 100 =37.5. Option C.

Sorry about the oversight guys. Have edited my post. Cheers!

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