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What percent of the solution is water?

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What percent of the solution is water? [#permalink]

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New post 27 Jan 2017, 09:38
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What percent of the solution is water?

(1) Adding 5 liters of water increases the percentage of water by 20%.
(2) There are 30 liters of solution before any additions or subtractions from the solution.
[Reveal] Spoiler: OA

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Re: What percent of the solution is water? [#permalink]

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New post 28 Jan 2017, 14:44
assume there is W liter water in S liter of solution therefore (W/S)=?

1. assume there is W liter water in S liter solution the percentage is (W/S)*100 after adding a 5 liter of water there is S+5 liter of solution and W+5 of water. algebraically we can write (W+5)/(S+5)=(W/S)+.2* (20 percent increase is equal to .2) it is clear that there is no way to solve for w/s. insuff

2. S=30. clearly insufficient

1+2. having S=30 we can solve for w from * then W/S. Sufficient.
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Re: What percent of the solution is water? [#permalink]

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New post 20 Feb 2017, 02:09
Bunuel wrote:
What percent of the solution is water?

(1) Adding 5 liters of water increases the percentage of water by 20%.
(2) There are 30 liters of solution before any additions or subtractions from the solution.



Bunuel,

Need your help here. Is option A not clear-I can get a unique solution in which we have 25 litres of water in a 30 litre solution and adding 5 litres increases the % of water by 20%.
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Re: What percent of the solution is water? [#permalink]

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New post 10 Apr 2018, 22:38
Bunuel wrote:
What percent of the solution is water?

(1) Adding 5 liters of water increases the percentage of water by 20%.
(2) There are 30 liters of solution before any additions or subtractions from the solution.



Initial conc. of water = W1 - To be found
Final conc. of water = W2
Initial volume of mixture = V1
Final volume of mixture = V2

Ci * Vi = Cf * Vf

St-1:
W1 = ?
W2 = 20%
V1 = ?
V2 = V1+5

W1 * V1 = 20 * (V1+5)

After simplification: W1 = 20 + (5/V1)

V1 can have multiple values. Hence, St-1 NS.

St-2:
W1 = ?
W2 = ?
V1 = 30
V2 = ?

W1 * 30 = W2 * V2
Hence, St-2 NS.

St-1 + St-2:
W1 = 20 + (5/V1)
V1 = 30

We get unique W1.

Therefore, answer is (C) (St-1 + St-2)
Re: What percent of the solution is water?   [#permalink] 10 Apr 2018, 22:38
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