|
|
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.
08 Aug 2023, 01:30
Kudos
Bookmarks
E
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
15%
(low)
Question Stats:
82% (00:59) correct
18%
(02:09)
wrong
based on 137
sessions
History
Date
Time
Result
Not Attempted Yet
How many liters of 20% vinegar solution should be added to 4 liters of 50% vinegar solution to make a 30% vinegar solution?
A. 1
B. 2
C. 4
D. 6
E. 8
A. 1
B. 2
C. 4
D. 6
E. 8
08 Aug 2023, 04:59
Kudos
Bookmarks
Weighted average.
2+0.2x/4+x=0.3
2+0.2x=1.2+0.3x
x=8
2+0.2x/4+x=0.3
2+0.2x=1.2+0.3x
x=8
08 Aug 2023, 06:16
Kudos
Bookmarks
Bunuel
Using weighted averages:
\(\frac{w1}{w2} = \frac{(A2 - Avg)}{(Avg - A1)}\)
\(\frac{w1}{w2 }= \frac{(50 - 30)}{(30 - 20)} = \frac{2}{1}\)
Hence for every 2 parts of 20% solution we have 1 part of 50% solution.
Since we have 4 litres of 50% solution, we must have added 8 litres of 20% solution.
Answer (E)
Or we can use the scale method to visualise the answer:
20 ------30 ------------------- 50
Since distance is in the ratio 1:2, the weights will be in the ratio 2:1 for 20% and 50% solution respectively. Since we have 4 litres of 50% solution, we must have added 8 litres of 20% solution.
Check Weighted Avg and Mixtures Basics in these posts:
https://anaprep.com/arithmetic-weighted-averages/
https://anaprep.com/arithmetic-mixtures/
and these videos:
https://www.youtube.com/watch?v=_GOAU7moZ2Q
https://www.youtube.com/watch?v=VdBl9Hw0HBg
