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02 May 2019, 02:30
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C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
35%
(medium)
Question Stats:
75% (02:14) correct
25%
(02:42)
wrong
based on 138
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An alloy of copper and nickel contains 65 % copper. A second alloy contains copper and nickel in the ratio 17 : 3. In what ratio should the two alloys be mixed so that the new mixture contains 4 times as much copper as nickel?
A. 4 : 5
B. 5 : 4
C. 1 : 3
D. 2 : 3
E. None of these
A. 4 : 5
B. 5 : 4
C. 1 : 3
D. 2 : 3
E. None of these
02 May 2019, 02:54
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We are mixing a 65% copper alloy with an 85% copper alloy (17/20 = 85%) and want to arrive at an 80% alloy (4/5 = 80%). Putting these three 'averages' on a number line:
--65---------------80-----85----
the ratio of the two components must equal the ratio of the two distances to the middle average of 80, so they must be mixed in a 15 to 5, or 3 to 1 ratio. Since we need to use more of the 85% alloy (since 80 is closer to 85 than it is to 65), we need to mix the 65% alloy and the 85% alloy in a 1 to 3 ratio.
There's a problem with the wording of the question -- it isn't clear whether the answer should be 1 to 3 or 3 to 1, since the question doesn't tell us which of the two alloys is supposed to go first in this ratio.
--65---------------80-----85----
the ratio of the two components must equal the ratio of the two distances to the middle average of 80, so they must be mixed in a 15 to 5, or 3 to 1 ratio. Since we need to use more of the 85% alloy (since 80 is closer to 85 than it is to 65), we need to mix the 65% alloy and the 85% alloy in a 1 to 3 ratio.
There's a problem with the wording of the question -- it isn't clear whether the answer should be 1 to 3 or 3 to 1, since the question doesn't tell us which of the two alloys is supposed to go first in this ratio.
02 May 2019, 06:51
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Let C1 be the copper in first alloy and C2 be the copper in second alloy. It is given that C1=65%
And from the ratio of C2:N2=17:3, we can say that C2=85%.
The copper in mixture of two alloys should be 4 times that of nickel, that is C = 4N, and from this ratio we can say that copper in resultant mixture should be 80%.
We have % of copper in two allows and the desired %, therefore applying allegation method
C2---85--------------15
--------------80--------
C1---65---------------5
Therefore, C1:C2=5:15=1:3
OA - C
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Kudos if helpful!
And from the ratio of C2:N2=17:3, we can say that C2=85%.
The copper in mixture of two alloys should be 4 times that of nickel, that is C = 4N, and from this ratio we can say that copper in resultant mixture should be 80%.
We have % of copper in two allows and the desired %, therefore applying allegation method
C2---85--------------15
--------------80--------
C1---65---------------5
Therefore, C1:C2=5:15=1:3
OA - C
-------------------
Kudos if helpful!
