hemant_rajput wrote:Q10 . Brass is an alloy of copper and zinc. Bronze is an alloy containing 80% of copper, 4% of zinc and 16% of tin. A fused mass of brass and bronze is found to contain 74% of copper,16% of zinc and 10% of tin. The ratio of copper to zinc in brass is:
a. 64 and 36
b. 33 and 67
c. 50 and 50
d. 35 and 65
e. None of these
[spoiler]oa:a[/spoiler]
Use ALLIGATION to determine the ratio of brass to bronze in the fused mass.
Brass = 0% tin.
Bronze = 16% tin.
Fused mass = 10% tin.
Step 1: Plot the 3 percentages on a number line, with the percentages in brass and bronze (0% and 16%) on the ends and the percentage in the fused mass (10%) in the middle.
Brass 0%----------------10%-------------------16% Bronze
Step 2: Calculate the distances between the percentages.
Brass 0%--------
10------10%-------
6-----------16% Bronze
The ratio of the distances = 10:6 = 5x : 3x.
The ratio of the distances must be the same for COPPER.
Percentage of copper in the fused mass = 74%.
Percentage of copper in bronze = 80%.
Let the percentage of copper in brass = C.
Step 3: Plot the percentages for COPPER on the number line.
Brass C%--------
5x------74%-------
3x-----------80% Bronze
The number line above implies the following:
3x = 80-74
3x = 6
x=2.
Since 5x = 5*2 = 10, the distance between C and 74 = 10.
Thus, C = 74-10 = 64.
Thus, brass is 64% copper and 36% zinc.
The correct answer is
A.
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