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

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Manager
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Joined: 28 Jul 2011
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Salad dressing A is made up of 30% vinegar and 70% oil, and salad dres  [#permalink]

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New post 24 Aug 2011, 04:04
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  25% (medium)

Question Stats:

76% (01:43) correct 24% (02:34) wrong based on 318 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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Re: Salad dressing A is made up of 30% vinegar and 70% oil, and salad dres  [#permalink]

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New post 24 Aug 2011, 06:07
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5
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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Manager
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Joined: 27 Jul 2010
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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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New post 24 Aug 2011, 05:53
3
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%
Manager
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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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New post 24 Aug 2011, 06:13
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]

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New post 24 Aug 2011, 11:05
3
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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Manager
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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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New post 25 Aug 2011, 04:23
Thank everyone, appreciate your help. those were some really good short hands.

Regards,
Manager
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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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New post 08 Sep 2011, 08:59
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]

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New post 19 Oct 2014, 21:05
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%


Here is a post that discusses how to solve such questions in seconds: http://www.veritasprep.com/blog/2011/04 ... -mixtures/
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)
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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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New post 22 Feb 2018, 16:34
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 &nbs [#permalink] 22 Feb 2018, 16:34
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