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A certain tank is filled to one quarter of its capacity with a mixture

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A certain tank is filled to one quarter of its capacity with a mixture  [#permalink]

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New post 30 Sep 2014, 07:51
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A certain tank is filled to one quarter of its capacity with a mixture consisting of water and sodium chloride. The proportion of sodium chloride in the tank is 40% by volume and the capacity of the tank is 24 gallons. If the water evaporates from the tank at the rate of 0.5 gallons per hour, and the amount of sodium chloride stays the same, what will be the concentration of water in the mixture in 2 hours?

A. 43%
B. 50%
C. 52%
D. 54%
E. 56%

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Re: A certain tank is filled to one quarter of its capacity with a mixture  [#permalink]

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New post 30 Sep 2014, 21:54
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Bunuel wrote:
A certain tank is filled to one quarter of its capacity with a mixture consisting of water and sodium chloride. The proportion of sodium chloride in the tank is 40% by volume and the capacity of the tank is 24 gallons. If the water evaporates from the tank at the rate of 0.5 gallons per hour, and the amount of sodium chloride stays the same, what will be the concentration of water in the mixture in 2 hours?

A. 43%
B. 50%
C. 52%
D. 54%
E. 56%


The tank of 24 gallons is filled to a quarter so it had 6 gallons of water with 40% sodium chloride. In 2 hrs, .5*2 = 1 gallon of pure water (0% sodium chloride) will evaporate.
In essence, the initial mix of 6 gallons (40% sodium chloride) was a mix of 5 gallons of x% sodium chloride and 1 gallon of pure water.

Working with sodium chloride concentrations:
w1/w2 = (A2 - Aavg)/(Aavg - A1)
5/1 = (0 - 40)/(40 - x)
x = 48

So concentration of water is 100 - 48 = 52%
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Re: A certain tank is filled to one quarter of its capacity with a mixture  [#permalink]

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New post 30 Sep 2014, 18:38
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Answer = C = 52%

NaCl................... Water ................. Total

2.4 ......................... 3.6 ....................... 6

Post evaporation

2.4 ........................... 2.6 ......................... 5

Percentage \(= \frac{2.6}{5} * 100 = 52%\)
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Re: A certain tank is filled to one quarter of its capacity with a mixture  [#permalink]

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New post 09 Jan 2015, 09:48
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Bunuel wrote:
A certain tank is filled to one quarter of its capacity with a mixture consisting of water and sodium chloride. The proportion of sodium chloride in the tank is 40% by volume and the capacity of the tank is 24 gallons. If the water evaporates from the tank at the rate of 0.5 gallons per hour, and the amount of sodium chloride stays the same, what will be the concentration of water in the mixture in 2 hours?

A. 43%
B. 50%
C. 52%
D. 54%
E. 56%


c -

initial 40% sodium = 2.4 & 60 % water = 3.6

after 2 hours- evaporating at the rate of .5/hr

sodium -2.4 [Remain same - stated],water -2.6

c- 52%

Hope i deserve some kudos :)
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Re: A certain tank is filled to one quarter of its capacity with a mixture  [#permalink]

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New post 09 Jan 2015, 22:53
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Tank is filled 1/4 of its capacity

Solution = 1/4 * 24 = 6

Sodium = 0.4 * 6 = 2.4
Water = 6-2.4 = 3.6

Evaporation Process

0 hour - 3.6
1 hour - 3.1
2 hour - 2.6

or you can simply subtract 1 from 3.6

quantity of new solution = sodium + water = 2.4 + 2.6 = 5

Concentration of water = (2.6/5) * 100 = 52%
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Re: A certain tank is filled to one quarter of its capacity with a mixture  [#permalink]

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New post 22 Oct 2016, 07:42
Here is how I did it. My mistake when i first tried it was forgetting that the tank is 1/4 full and that i needed to divide 24/4 in order to get the correct solution.

step1) (1/4) 24 = 6
step2) 6*(.40) =SC = 2.4 and 6*(.6) = W = 3.6 = total = 6
step3) 0.5*2 = 1 => 6-1 = 5 new total => 3.6 -1 = 2.6 new water
step4) 2.6/5 => (2.6*2)/(5*2) = 5.2/10 = 0.52.
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Re: A certain tank is filled to one quarter of its capacity with a mixture  [#permalink]

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New post 12 Nov 2016, 00:46
Bunuel wrote:
A certain tank is filled to one quarter of its capacity with a mixture consisting of water and sodium chloride. The proportion of sodium chloride in the tank is 40% by volume and the capacity of the tank is 24 gallons. If the water evaporates from the tank at the rate of 0.5 gallons per hour, and the amount of sodium chloride stays the same, what will be the concentration of water in the mixture in 2 hours?

A. 43%
B. 50%
C. 52%
D. 54%
E. 56%


SINCE THE amount of SC didn't change we can use the formula (C final = C initial * V initial/V final)

Cf = 0.4* (6/5.5)*(5.5/5) = 48% and thus water concentration in final mix is 100%-48% 52%
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Re: A certain tank is filled to one quarter of its capacity with a mixture  [#permalink]

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New post 07 Dec 2017, 15:07
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: A certain tank is filled to one quarter of its capacity with a mixture &nbs [#permalink] 07 Dec 2017, 15:07
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