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A solution of 27 gallons of acid contains 9 gallons of pure acid. How

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Bunuel
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A solution of 27 gallons of acid contains 9 gallons of pure acid. How [#permalink] New post   03 Jan 2022, 08:45
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A solution of 27 gallons of acid contains 9 gallons of pure acid. How much water in gallons, should be added to produce a 25 percent solution of this acid?

(A) 6 3/4
(B) 9
(C) 15 3/4
(D) 18
(E) 27
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B
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Charli08
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A solution of 27 gallons of acid contains 9 gallons of pure acid. How [#permalink] New post   04 Jan 2022, 01:27
Quickest way is to try answer choices. Since they are of increasing value try choice B then choice D.

**Idea behind this: If B is too big then the answer is A. If D is too big the answer is C if D is too small the answer is D. Obviously is either B or D gets you the right answer then it is the right answer.

So using B we add 9 to the denominator as that is the total volume:

9/25+9 = 9/36 = 1/4

==> B
We don't need to test anymore.
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Re: A solution of 27 gallons of acid contains 9 gallons of pure acid. How [#permalink] New post   20 Jan 2022, 01:51
A solution of 27 gallons of acid contains 9 gallons of pure acid. How much water in gallons, should be added to produce a 25 percent solution of this acid?

9gl - acid
18gl - water or 1/3 acid + 2/3 water

(18+y)/(27+y)=3/4
72+4y=81+3y
y=9

Ans B.
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Re: A solution of 27 gallons of acid contains 9 gallons of pure acid. How [#permalink] New post   07 Jan 2024, 11:54
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Since 9 gallons of 100% acid
and a total volume of 27 gallons, the current ratio of acid is 9 gallons (100% acid)/ 27 gallons total = 1/3

What volume of water [since you can't add more acid to bring down the %] is needed to make the new ratio 1/4 [25%]

X will be the volume of water to be added
9 gallons / (27+X) = 1/4
4 * 9 gallons = (27 + X)
36 = 27 + X
9 = X
therefore, you need to add 9 gallons of water
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Re: A solution of 27 gallons of acid contains 9 gallons of pure acid [#permalink] New post   04 Mar 2024, 10:34
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Re: A solution of 27 gallons of acid contains 9 gallons of pure acid [#permalink]
04 Mar 2024, 10:34
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