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Bunuel
A certain amount of 8% copper ore was mixed with another amount of 3% coper ore to produce 300 tons of 6% coper ore. How many tons of the 8% coper ore were used to make this mixture?

A. \(81\frac{9}{11}\)

B. \(112\frac{1}{2}\)

C. 120

D. \(163\frac{7}{11}\)

E. 180

The copper percentage of the mixture is the weighted arithmetic average of the copper percentages of its components, so we have:

[(x)8 + (300 – x)3]/300 = 6

(x)8 + (300 – x)3 = 1,800

8x + 900 – 3x = 1,800

5x = 900

x = 180

Answer: E
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Bunuel
A certain amount of 8% copper ore was mixed with another amount of 3% coper ore to produce 300 tons of 6% coper ore. How many tons of the 8% coper ore were used to make this mixture?

A. \(81\frac{9}{11}\)

B. \(112\frac{1}{2}\)

C. 120

D. \(163\frac{7}{11}\)

E. 180
­let A and B be the total amount of 8% and 3% ore
8/100A + 3/100 B = 6%300
8A + 3B = 1800-----(1)
A+B = 300 ------(2)
solve 1 and 2 
a= 180
answer E
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Bunuel
A certain amount of 8% copper ore was mixed with another amount of 3% copper ore to produce 300 tons of 6% copper ore. How many tons of the 8% copper ore were used to make this mixture?

A. \(81\frac{9}{11}\)

B. \(112\frac{1}{2}\)

C. 120

D. \(163\frac{7}{11}\)

E. 180
8% mixed with 3% to give 6% resultant. Use the weighted averages formula

\(\frac{w1}{w2} = \frac{(A2 - Aavg)}{(Aavg - A1)} = \frac{(8-6)}{(6-3)} = \frac{2}{3}\)

So amount of 3% ore : amount of 8% ore = 2 : 3

So 8% ore was 3/5th of the total 300 tons i.e. 180 tons

Answer (E)

Weighted Avg and Mixtures Basics:
https://anaprep.com/arithmetic-weighted-averages/
https://anaprep.com/arithmetic-mixtures/
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