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Let's assume that the amount of mixture is x ounces.
Given that 30% of the mixture is vinegar, i.e. amount of vinegar in original mixture = (30/100)x = (3/10)x. Therefore, the amount of oil = (7/10)x
Now 10 ounces of oil was added to the mixture, the resulting new mixture was only 18% vinegar
Amount of Vinegar = (3/10)x
Amount of Oil = (7/10)x + 10
Therefore, (3/10)x/(x+10) = 18/100
3x/(x+10) = 9/5
x/(x+10) = 3/5
5x = 3x + 30
2x = 30
x = 15

Hence, the correct answer is Option A. 15
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rkgp90
A different mixture of vinegar and oil was 30 percent vinegar. After 10 ounces of oil was added to the mixture, the resulting new mixture was only 18 percent vinegar. How many ounces were in the original mixture?

A. 15
B. 16
C. 17
D. 18
E. 19

let x=ounces in original mixture
.7x+10=.82(x+10)
x=15
A
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rkgp90
A different mixture of vinegar and oil was 30 percent vinegar. After 10 ounces of oil was added to the mixture, the resulting new mixture was only 18 percent vinegar. How many ounces were in the original mixture?

A. 15
B. 16
C. 17
D. 18
E. 19

We can let n = the total number of ounces of the mixture.

Thus, 0.3n = amount of vinegar and 0.7n = amount of oil.

We are given that after 10 ounces of oil was added to the mixture, the new mixture was 18 percent vinegar. So we can create the following equation to determine n:

0.3n/(n + 10) = 18/100

0.3n x 100 = 18(n + 10)

30n = 18n + 180

12n = 180

n = 15

So originally there were 15 ounces in the mixture.

Alternate Solution:

We start with x ounces of 30% vinegar, and we add 10 ounces of 0% vinegar, to get (x + 10) ounces of 18% vinegar. We can create the equation:

0.30x + (0)(10) = (x + 10)0.18

0.30x = 0.18x + 1.8

0.12x = 1.8

12x = 180

x = 15

The initial amount of mixture was 15 ounces.

Answer: A
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rkgp90
A different mixture of vinegar and oil was 30 percent vinegar. After 10 ounces of oil was added to the mixture, the resulting new mixture was only 18 percent vinegar. How many ounces were in the original mixture?

A. 15
B. 16
C. 17
D. 18
E. 19

Hi,

Two ways to solve this problem.
1:
0%|-----------------18%-------|30%
Vinegar----------resultant------Vinegar
10oz-------------dont know-----need to find out
w1---------------dont care------w2

Now, from weighted average
(w1/w2) = (A2-Avg)/(Avg-A1)
10/w2 = (30-18)/(18-0)
w2=15oz

2:
Since Amount of vinegar does not change after adding 10oz of oil. we can say that,
CiVi = CfVf
Initial concentration * Initial Volume = Final Concentration * Final Volume
(0.3)Vi = (0.18)(Vi+10)
0.3Vi = 0.18Vi + 1.8
Vi = 1.8/0.12 = 15 Oz
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x grams = vinegar + oil
30% = vinegar = (30/100)*x grams
70% = oil = (70/100)*x grams

x + 10grams = vinegar + oil + 10grams

as oil was added to the mixture, therefore the amount of vinegar in grams in the mixture remains the same.

18% = vinegar = (18/100)*(x+10) grams = (30/100)*x grams
18x + 180 = 30x
therefore x = 15 g
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