|
|
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized
for You
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
02 May 2019, 02:30
Kudos
Bookmarks
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:
76% (02:11) correct
24%
(02:41)
wrong
based on 177
sessions
History
Date
Time
Result
Not Attempted Yet
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
Kudos
Bookmarks
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
Kudos
Bookmarks
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
-------------------
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!
