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A solution that is 40% acid must be strengthened to become a solution

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A solution that is 40% acid must be strengthened to become a solution [#permalink]

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A solution that is 40% acid must be strengthened to become a solution that is 88% acid. If there are 10 ounces of the 40% solution, how much pure acid must be added?

A. 2.5 ounces
B. 18 ounces
C. 28 ounces
D. 40 ounces
E. 48 ounces
[Reveal] Spoiler: OA

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Re: A solution that is 40% acid must be strengthened to become a solution [#permalink]

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New post 19 Mar 2017, 13:51
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In the original Solution of 10 ounces, Acid content is 40%, i.e. 4 ounces

To make this this solution 88% acidic, let the amount of acid added is x ounces.

(4+x)/(10+x) = 0.88

Solving for X, gives x as 40.

Answer is D. 40 ounces

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Re: A solution that is 40% acid must be strengthened to become a solution [#permalink]

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Bunuel wrote:
A solution that is 40% acid must be strengthened to become a solution that is 88% acid. If there are 10 ounces of the 40% solution, how much pure acid must be added?

A. 2.5 ounces
B. 18 ounces
C. 28 ounces
D. 40 ounces
E. 48 ounces

let the pure acid to be added be x

initially, 10 ounce has 40% = 4 ounce acid and 60% = 6 ounce rest of the stuff
finally 10+x ounce has 88% acid and 12% = 0.12(10+x) ounce rest of the stuff

since rest of the stuff will remain equal in both cases, thereofore

0.12(10+x) = 6

or x = 40 ounce

Option D

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A solution that is 40% acid must be strengthened to become a solution [#permalink]

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New post 22 May 2017, 12:21
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If we add 10 oz of 100% solution, we will have a 60% mixture. Answer A out
If we add 20 oz of 100% solution, we will have an 80% mixture. Answer B out.

Further, we can use weighted average :

40---------------88------100

Distance between 88 and 40 is 48
Distance between 88 and 100 is 12

Ratio of 40% sol to 100% sol in the mixture is 12:48 or 1:4
So, the mixture will consist of 1 ratio unit of 40% sol and 4 ratio units of 100% sol. One ratio unit is 10, therefore 4 x 10 = 40.
Answer D

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Re: A solution that is 40% acid must be strengthened to become a solution [#permalink]

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New post 22 May 2017, 13:26
Bunuel wrote:
A solution that is 40% acid must be strengthened to become a solution that is 88% acid. If there are 10 ounces of the 40% solution, how much pure acid must be added?

A. 2.5 ounces
B. 18 ounces
C. 28 ounces
D. 40 ounces
E. 48 ounces


let x=ounces of acid to be added
.4*10+x=.88(10+x)
x=40 ounces
D

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Re: A solution that is 40% acid must be strengthened to become a solution [#permalink]

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New post 17 Jun 2017, 02:53
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Bunuel wrote:
A solution that is 40% acid must be strengthened to become a solution that is 88% acid. If there are 10 ounces of the 40% solution, how much pure acid must be added?

A. 2.5 ounces
B. 18 ounces
C. 28 ounces
D. 40 ounces
E. 48 ounces


We need to make 40% acid solution into a 88% acid solution.

A1 = 40% Acid Solution
A2 = 100% Acid Solution (Pure Acid)
Final = 88% Acid Solution

A1:A2 = 1:4
If we have 10 ounces of A1, we need to have 40 ounces of A2.

Hence D :)

Thank you Karishma for the weighted average method.
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Re: A solution that is 40% acid must be strengthened to become a solution [#permalink]

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New post 13 Oct 2017, 21:48
Ballparking, 48 is impossible because the acidic will be more than 88%, a little lesser than 48, which is 40 Answer D.

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Re: A solution that is 40% acid must be strengthened to become a solution   [#permalink] 13 Oct 2017, 21:48
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