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A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters

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Bunuel
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A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters [#permalink] New post   11 Mar 2020, 04:30
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A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters of water is added, what is the new concentration of alcohol, as a percent of volume?

(A) 5%
(B) 10%
(C) 12%
(D) 12.5%
(E) 16%
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E
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BrentGMATPrepNow
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Re: A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters [#permalink] New post   11 Mar 2020, 06:05
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Bunuel wrote:
A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters of water is added, what is the new concentration of alcohol, as a percent of volume?

(A) 5%
(B) 10%
(C) 12%
(D) 12.5%
(E) 16%


A 400 milliliter solution is 20% alcohol by volume.
20% of 400 = 80
So, the original solution contains 80 milliliters of alcohol

If 100 milliliters of water is added...
400 + 100 = 500
So, our NEW solution has a total volume of 500 milliliters

...what is the new concentration of alcohol, as a percent of volume?
NEW concentration of alcohol = 80/500
Divide top and bottom of our fraction by 5 to get: 16/100, which is the same as 16%

Answer: E

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Brent
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Re: A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters [#permalink] New post   11 Mar 2020, 10:11
Bunuel wrote:
A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters of water is added, what is the new concentration of alcohol, as a percent of volume?

(A) 5%
(B) 10%
(C) 12%
(D) 12.5%
(E) 16%


Water = 80% of 400 => 320
Alcohol = 20% of 400 => 80

Total Mixture = 400

After adding 100 ml of water -

Water = 80% of 400 +100 => 420
Alcohol = 20% of 400 => 80

Total Mixture = 500

So, the new concentration of alcohol, as a percent of volume?

= 80/500*100

= 16%, Thus Answer must be (E)
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Re: A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters [#permalink] New post   11 Mar 2020, 11:05
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Bunuel wrote:
A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters of water is added, what is the new concentration of alcohol, as a percent of volume?

(A) 5%
(B) 10%
(C) 12%
(D) 12.5%
(E) 16%


Solution


    • Total volume of the solution = 400 ml
    • 20% of the solution by volume is alcohol.
      o So, volume of alcohol \(= \frac{20}{100}*400 = 80\) ml
    • Since 100 ml water is added, so new total volume of the solution \(= 400 + 100 = 500\) ml
    • Therefore, alcohol % by volume = (volume of alcohol/ total volume of the solution) \(*100 = \frac{80}{500}*100 = 16\)%
Thus, the correct answer is Option E.
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Re: A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters [#permalink] New post   17 Jan 2021, 12:21
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Bunuel wrote:
A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters of water is added, what is the new concentration of alcohol, as a percent of volume?

(A) 5%
(B) 10%
(C) 12%
(D) 12.5%
(E) 16%

Solution:

If a 400-milliliter solution is 20% alcohol by volume, it has 400 x 0.2 = 80 milliliters of alcohol. Thus the concentration of alcohol, when 100 milliliters of water is added, is:

80 / (400 + 100) = 80/500 = 16/100 = 16%

Alternate Solution:

To a 400-ml solution of 20% alcohol, we add 100 ml of water, which has 0% alcohol, and we obtain 500 ml of a solution with x% alcohol. Creating an equation, we have:

400 (0.20) + 100 (0) = 500x

80 + 0 = 500x

0.16 = x

Converted to a percent, we see that x = 16%.


Answer: E
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Re: A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters [#permalink] New post   02 Sep 2021, 10:07
hey GMATBusters kindly help in these question with alligation
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Re: A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters [#permalink] New post   03 Sep 2021, 08:18
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Hi

you can do this question by alligation as described in the sketch, Feel free to tag me again for any doubt.



DIPU226 wrote:
hey GMATBusters kindly help in these question with alligation

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Re: A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters [#permalink] New post   17 Dec 2022, 06:28
Hello from the GMAT Club BumpBot!

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Re: A 400 milliliter solution is 20% alcohol by volume. If 100 milliliters [#permalink]
17 Dec 2022, 06:28
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