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Salad dressing A is made up of 30% vinegar and 70% oil, and salad dres

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kuttingchai
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Salad dressing A is made up of 30% vinegar and 70% oil, and salad dres [#permalink] New post   24 Aug 2011, 05:04
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25% (medium)

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76% (01:36) correct 24% (02:15) wrong based on 599 sessions
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Salad dressing A is made up of 30% vinegar and 70% oil, and salad dressing B contains 10% vinegar and 90% oil. If the 2 dressing are combined to produce a salad dressing that is 15% vinegar, dressing A comprises what % of the new dressing?

A. 15%
B. 20%
C. 25%
D. 40%
E. 55%
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C
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walker
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Re: Salad dressing A is made up of 30% vinegar and 70% oil, and salad dres [#permalink] New post   24 Aug 2011, 07:07
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There is one trick you can use to solve mixture problems very fast.

quantity of Vinegar in A: 30%, in B: 10% and in (A+B): 15%

We need (15-10)/(30-10) = 5/20 = 1/4 or 25% of A.
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Salad dressing A is made up of 30% vinegar and 70% oil, and salad dres [#permalink] New post   Updated on: 17 Oct 2022, 01:06
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kuttingchai wrote:
Salad dressing A is made up of 30% vinegar and 70% oil, and salad dressing B contains 10% vinegar and 90% oil. If the 2 dressing are combined to produce a salad dressing that is 15% vinegar, dressing A comprises what % of the new dressing?

A. 15%
B. 20%
C. 25%
D. 40%
E. 55%



The copper nickel example is exactly like this one.

w1/w2 = (A2 - Aavg)/(Aavg - A1)
wA/wB = (10 - 15)/(15 - 30) = 1/3

So ratio of salad dressing A to salad dressing B is 1:3 i.e. salad dressing A makes up 1/4 = 25% of the mix.
Answer (C)

Originally posted by KarishmaB on 19 Oct 2014, 22:05.
Last edited by KarishmaB on 17 Oct 2022, 01:06, edited 1 time in total.
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omnikey
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Re: Salad dressing A is made up of 30% vinegar and 70% oil, and salad dres [#permalink] New post   24 Aug 2011, 06:53
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they way I solved it:
quantity of Vinegar => 30% A + 10% B = 15% (A + B)
30%A + 10%B = 15%A + 15%B
15%A = 5%B
B = 15%A / 5% = 3A
if B = 3A => A+B = 4A
as a result A / (A+B) = A / 4A = 0.25 = 25%
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Re: Salad dressing A is made up of 30% vinegar and 70% oil, and salad dres [#permalink] New post   24 Aug 2011, 07:13
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use the graph method to solve it quickly

B has 30% vinegar, A - 10% and the new dressing - 15%
---10-----15-----------------30
therefore intuitively you can say that there is a lot less of dressing A than dressing B in the new mix since 15 is closer to 10 than 30 is. How much lesser? (15-10)/(30-10) = 5/20 = 25%
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Re: Salad dressing A is made up of 30% vinegar and 70% oil, and salad dres [#permalink] New post   24 Aug 2011, 12:05
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The total combination must be 100%. Let X% of dressing 1 is used.
30 * x + 10 * (100-x) = 15*100
solving, x= 25%
C is the answer.
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Re: Salad dressing A is made up of 30% vinegar and 70% oil, and salad dres [#permalink] New post   25 Aug 2011, 05:23
Thank everyone, appreciate your help. those were some really good short hands.

Regards,
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Re: Salad dressing A is made up of 30% vinegar and 70% oil, and salad dres [#permalink] New post   08 Sep 2011, 09:59
alexgmd wrote:
they way I solved it:
quantity of Vinegar => 30% A + 10% B = 15% (A + B)
30%A + 10%B = 15%A + 15%B
15%A = 5%B
B = 15%A / 5% = 3A
if B = 3A => A+B = 4A
as a result A / (A+B) = A / 4A = 0.25 = 25%


This is how I worked it out.

Walker, can you please explain your method a bit?
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Re: Salad dressing A is made up of 30% vinegar and 70% oil, and salad dres [#permalink] New post   22 Feb 2018, 17:34
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kuttingchai wrote:
Salad dressing A is made up of 30% vinegar and 70% oil, and salad dressing B contains 10% vinegar and 90% oil. If the 2 dressing are combined to produce a salad dressing that is 15% vinegar, dressing A comprises what % of the new dressing?

A. 15%
B. 20%
C. 25%
D. 40%
E. 55%


We can let the amount of dressing A = a and the amount of dressing B = b, thus:

0.3a + 0.1b = 0.15(a + b)

30a + 10b = 15a + 15b

15a = 5b

3a = b

So dressing A is a/(a + b) = a/(a + 3a) = 1/4 = 25% of the new dressing.

Answer: C
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Re: Salad dressing A is made up of 30% vinegar and 70% oil, and salad dres [#permalink] New post   14 Feb 2024, 06:30
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Re: Salad dressing A is made up of 30% vinegar and 70% oil, and salad dres [#permalink]
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