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Intern  Joined: 19 Dec 2009
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Solution Y is 30 percent liquid X and 70 percent water. If 2 kilogram  [#permalink]

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Difficulty:   45% (medium)

Question Stats: 71% (02:41) correct 29% (02:44) wrong based on 708 sessions

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Solution Y is 30 percent liquid X and 70 percent water. If 2 kilograms of water evaporate from 8 kilograms of solutions Y and 2 kilograms of solution Y are added to the remaining 6 kilograms of liquid, what percent of this new liquid solution is liquid X?

A. 30%
B. 33 1/3%
C. 37 1/2%
D. 40%
E. 50%

Project PS Butler : Question #106

Math Expert V
Joined: 02 Sep 2009
Posts: 61396
Re: Solution Y is 30 percent liquid X and 70 percent water. If 2 kilogram  [#permalink]

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rovshan85 wrote:
Solution Y is 30% liquid X and 70 percent water. If 2 kilograms of water evaporate from 8 kg of solution Y and 2 kg of solution Y are added to the remaining 6 kg of liquid, what percent of this new solution is liquid X?

a. 30
b. 33 1/3
c. 37 1/2
d. 40
e. 50

What is the easiest way to approach this type of problem and solve under 2 min.

In 8 kilograms of solution Y there are 0.3*8=2.4 kilograms of solution X;

After 2 kilograms of water are replaced by 2 kilograms of solution Y, to the existing 2.4 kilograms of solution X, 0.3*2=0.6 kilograms of solution X are added, so in the new solution of 8 kilograms there are 2.4+0.6=3 kilograms of solution X, which is 3/8*100=37.5% of this new solution.

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Intern  Joined: 24 Aug 2010
Posts: 5
Re: Solution Y is 30 percent liquid X and 70 percent water. If 2 kilogram  [#permalink]

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At the beggining, you have 8KG of solution Y, i.e.

70% * 8KG = 5,6 KG of Water
30% * 8KG = 2,4 KG of X

2KG of water evaporate:

5,6KG - 2KG = 3,6KG of Water
2,4KG of X

3,6KG + 2*0,70 = 5KG of Water
2,4KG + 2*0,30 = 3 KG of X

So you have 3KG of X in 8KG (3 + 5) solution.
Therefore X concentration is 3/8 = 37,5%
##### General Discussion
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Re: Solution Y is 30 percent liquid X and 70 percent water. If 2 kilogram  [#permalink]

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1
Took time to solve this one, the statement 2 kilograms of solution Y are added to the remaining 6 kilograms of liquid was confusing to me. After thinking more deeply, it was clear to me that new 2 kg of solution Y will also be 30% liquid X and 70% water, and then I was able to get the answer. That was a bit tricky and nice question.
Kudos +1 for posting the question Retired Moderator Joined: 02 Sep 2010
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Location: London
Re: Solution Y is 30 percent liquid X and 70 percent water. If 2 kilogram  [#permalink]

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Initially you start with 8kg of solution which has 2.4kg of X and 5.6kg of water
Post evaporation : 2.4kg of X and 3.6kg of water
Now we add back 2kg of Y --> 1.4Kg water + 0.6Kg X
So we have left 5Kg Water & 3Kg X

Percentage concentration is (3/5)*100 or 37.5%
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Re: Solution Y is 30 percent liquid X and 70 percent water. If 2 kilogram  [#permalink]

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shrouded1 wrote:
Initially you start with 8kg of solution which has 2.4kg of X and 5.6kg of water
Post evaporation : 2.4kg of X and 3.6kg of water
Now we add back 2kg of Y --> 1.4Kg water + 0.6Kg X
So we have left 5Kg Water & 3Kg X

Percentage concentration is (3/5)*100 or 37.5%

Yea, that's exactly how I solved but you know at first I was kinda adding 2 to 6 kg without considering liquid X and water's concentration within 2 kg being added.
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Re: Solution Y is 30 percent liquid X and 70 percent water. If 2 kilogram  [#permalink]

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1
Liquid x in 8 kg = 8*30%=12/5
Liquid x in next 2 kg = 2*30% = 3/5
Total x = 12/5 + 3/5 = 15/5 = 3
so, (3/8)*100= 37.5%
Ans. C
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Re: Solution Y is 30 percent liquid X and 70 percent water. If 2 kilogram  [#permalink]

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Initially we have 8kg of solution which has 3/10 0f 8= 2.4kg of X and 7/10 of 8 = 5.6kg of water after evaporation : 2.4kg of X and 3.6kg of water
Now we added 2kg of solution Y --> 7/10 of 2=1.4Kg water + 3/10 0f 2 =0.6Kg X
So we have left 5Kg Water & 3Kg X

Percentage concentration is (3/5)*100 or 37.5%
Manager  Joined: 28 Jul 2011
Posts: 153
Re: Solution Y is 30 percent liquid X and 70 percent water. If 2 kilogram  [#permalink]

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1
Solution Y total = 8
Liq x = 30% (8) = 2.4

Added 2 kg of Solution Y
Liq x = 30% (2) = 0.6

Final Solution wil have = (2.4 + 0.6) = 3 kg of Liq x

3/8 = 37.5%
Director  S
Joined: 17 Dec 2012
Posts: 620
Location: India
Re: Solution Y is 30 percent liquid X and 70 percent water. If 2 kilogram  [#permalink]

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1
rovshan85 wrote:
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 1/3%
C. 37 1/2%
D. 40%
E. 50%

What is the easiest way to approach this type of problem and solve under 2 min.

1. The net effect of 2 kg of water evaporating and adding 2 kg of the solution is removing (-2 + 1.4 = -0.6) 0.6 kg of water and adding 0.6 kg of liquid
2 Therefore the changed solution contains, 2.4 + 0.6 = 3 kg of liquid and 5.6-0.6==5 kg of water.
3. Percentage of liquid is 3/8 * 100 % = 37 1/2 %
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Re: Solution Y is 30 percent liquid X and 70 percent water. If 2 kilogram  [#permalink]

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rtaha2412 wrote:
Solution Y is 30 percent liquid X and 70 percent water. If 2 kilograms of water evaporate from 8 kilograms of solutions Y and 2 kilograms of solution Y are added to the remaining 6 kilograms of liquid, what percent of this new liquid solution is liquid X?

A. 30%
B. 33 1/3%
C. 37 1/2%
D. 40%
E. 50%

The best way to solve these problems is to take one step at a time

Initial:
8 kg Solution Y
This means Solution X = 2.4 kg, Water = 5.6 kg

Step 2:
2 kg of water is evaporated.
Left over: Solution X = 2.4 kg and Water = 3.6 kg

Step 3:
2 kg of Solutoin Y is added
Or, 0.6 kg of Solution X and 1.4 kg of water is added

Final:
Solution X = 3, Water = 5
% of solution X = 3/8 * 100 = 37.5%

Option C
Intern  Joined: 01 Feb 2016
Posts: 1
Re: Solution Y is 30 percent liquid X and 70 percent water. If 2 kilogram  [#permalink]

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rtaha2412 wrote:
Solution Y is 30 percent liquid X and 70 percent water. If 2 kilograms of water evaporate from 8 kilograms of solutions Y and 2 kilograms of solution Y are added to the remaining 6 kilograms of liquid, what percent of this new liquid solution is liquid X?

A. 30%
B. 33 1/3%
C. 37 1/2%
D. 40%
E. 50%

Hi,

I like using a table for mixture problems. This is what I came up with (see attachement):
Attachments Sol gmat.JPG [ 31.44 KiB | Viewed 11030 times ]

VP  P
Joined: 07 Dec 2014
Posts: 1233
Re: Solution Y is 30 percent liquid X and 70 percent water. If 2 kilogram  [#permalink]

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Solution Y is 30 percent liquid X and 70 percent water. If 2 kilograms of water evaporate from 8 kilograms of solutions Y and 2 kilograms of solution Y are added to the remaining 6 kilograms of liquid, what percent of this new liquid solution is liquid X?

A. 30%
B. 33 1/3%
C. 37 1/2%
D. 40%
E. 50%

let x=% of liquid X in new solution
.3*8+.3*2=x(6+2)
x=3/8=37.5%
C

Originally posted by gracie on 18 Jul 2016, 19:23.
Last edited by gracie on 28 Feb 2018, 21:08, edited 1 time in total.
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Re: Solution Y is 30 percent liquid X and 70 percent water. If 2 kilogram  [#permalink]

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DS00 wrote:
rtaha2412 wrote:
Solution Y is 30 percent liquid X and 70 percent water. If 2 kilograms of water evaporate from 8 kilograms of solutions Y and 2 kilograms of solution Y are added to the remaining 6 kilograms of liquid, what percent of this new liquid solution is liquid X?

A. 30%
B. 33 1/3%
C. 37 1/2%
D. 40%
E. 50%

Hi,

I like using a table for mixture problems. This is what I came up with (see attachement):

I also used the similar approach.
To Sum up:
Initial 8 kilograms of Y consist of 2.4 kg X and 5.6 kg water.
We then lose 2 kg water to evaporation, so we are down to 3.6 kg water.
The final step adds 2 kg Y, which consists of .6 kg X and 1.4 kg water.
Therefore, the final mixture contains 3 kg X and 5 kg water. 3/8 = 37.5%.
Intern  Joined: 31 Mar 2017
Posts: 8
Re: Solution Y is 30 percent liquid X and 70 percent water. If 2 kilogram  [#permalink]

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30% of 8 + 30% of 2 = 3 = X
X/T= 3/8 = 0.375 =37.5%

Posted from my mobile device
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Re: Solution Y is 30 percent liquid X and 70 percent water. If 2 kilogram  [#permalink]

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rtaha2412 wrote:
Solution Y is 30 percent liquid X and 70 percent water. If 2 kilograms of water evaporate from 8 kilograms of solutions Y and 2 kilograms of solution Y are added to the remaining 6 kilograms of liquid, what percent of this new liquid solution is liquid X?

A. 30%
B. 33 1/3%
C. 37 1/2%
D. 40%
E. 50%

Project PS Butler : Question #106

8 kg of the solution contains (8*0.3) kg = 2.4 kg of X

again,

2 kg of the add solution which is added will have 2*0.3 = 0.6 kg of X

Total final volume of the solution = 8 kg

Hence, % of X = (2.4+0.6)/8*100 = 3/8 * 100 =3* 12.5 = 37.5 %

Hence C)
Senior Manager  G
Joined: 12 Sep 2017
Posts: 313
Re: Solution Y is 30 percent liquid X and 70 percent water. If 2 kilogram  [#permalink]

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Hello!

Tricky question, these topics is very challenging for me.

Is it possible to solve it with weighted averages?

Kind regards!
Manager  S
Joined: 22 Sep 2018
Posts: 236
Re: Solution Y is 30 percent liquid X and 70 percent water. If 2 kilogram  [#permalink]

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rtaha2412 wrote:
Solution Y is 30 percent liquid X and 70 percent water. If 2 kilograms of water evaporate from 8 kilograms of solutions Y and 2 kilograms of solution Y are added to the remaining 6 kilograms of liquid, what percent of this new liquid solution is liquid X?

A. 30%
B. 33 1/3%
C. 37 1/2%
D. 40%
E. 50%

My reasoning:

8kg original solution is 30% X and 70% water or $$\frac{24}{10}kg liquid X and \frac{56}{10}kg water$$

Since we are looking for the percent of liquid X in our mixture we don't really care about the water in our solution.

We know that the total weight is 8kg and we are adding 2kg of solution Y, which has $$\frac{6}{10}kg liquid X$$.

$$\frac{24}{10} + \frac{6}{10} = 3kg$$ liquid X in the total solution.

$$\frac{3}{8} = 37.5%$$
VP  D
Joined: 09 Mar 2016
Posts: 1221
Re: Solution Y is 30 percent liquid X and 70 percent water. If 2 kilogram  [#permalink]

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1
rtaha2412 wrote:
Solution Y is 30 percent liquid X and 70 percent water. If 2 kilograms of water evaporate from 8 kilograms of solutions Y and 2 kilograms of solution Y are added to the remaining 6 kilograms of liquid, what percent of this new liquid solution is liquid X?

A. 30%
B. 33 1/3%
C. 37 1/2%
D. 40%
E. 50%

Project PS Butler : Question #106

Solution Y is 30 percent liquid X and 70 percent water

Total 8 litres

8 *0.3 = 2.4 kg liquid

5.6 kg = water

2 kilograms of water evaporate from 8 kilograms of solutions Y

so 5.6 -2 = 3.6 water is left

afterwards 2 kilograms of solution Y are added to the remaining 6 kilograms of liquid

Since, solution Y cosists of 30 percent is liquid X and 70 percent is water

hence 2 *0.3 = 0.6 kg is liquid and 2-0.4 = 1.4 is water

2.4 +0.6 = 3 kg liquid

3.6+1.4 = 5 kg water

what percent of this new liquid solution is liquid X?

$$\frac{3}{8} = 0.37$$ Target Test Prep Representative V
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Re: Solution Y is 30 percent liquid X and 70 percent water. If 2 kilogram  [#permalink]

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rtaha2412 wrote:
Solution Y is 30 percent liquid X and 70 percent water. If 2 kilograms of water evaporate from 8 kilograms of solutions Y and 2 kilograms of solution Y are added to the remaining 6 kilograms of liquid, what percent of this new liquid solution is liquid X?

A. 30%
B. 33 1/3%
C. 37 1/2%
D. 40%
E. 50%

Project PS Butler : Question #106

Originally, solution Y has 0.3 x 8 = 2.4 kg of liquid X and 0.7 x 8 = 5.6 kg of water. After 2 kg of water evaporate, solution Y has 2.4 kg of liquid X and 3.6 kg of water. However, since 2 kg of solution Y (of which, 0.3 x 2 = 0.6 kg is liquid X and 0.7 x 2 = 1.4 kg is water) are added back to the remaining 6 kilograms of solution Y, solution Y now has 2.4 + 0.6 = 3 kg of liquid X and 3.6 + 1.4 = 5 kg of water). Therefore, the percent of the new solution is liquid X is 3/(3 + 5) = 3/8 = 37.5%.

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