Events & Promotions
|
|
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.
Apr 2808:00 AM PDT
-11:00 AM PDT
Whether you are just beginning your MBA journey or fine-tuning your path to a 700+ score, GMAT Day is designed to give you a competitive edge.
04 May 2022, 08:15
Kudos
Bookmarks
B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
65%
(hard)
Question Stats:
68% (02:59) correct
32%
(03:11)
wrong
based on 234
sessions
History
Date
Time
Result
Not Attempted Yet
To do a certain work B would take three times as long as A and C together and C twice as long as A and B together. The three men complete the work together in 10 days. How long would each take separately?
A. 20, 60, 40
B. 24, 40, 30
C. 10, 90, 20
D. 12, 90, 18
E. 24, 80, 36
Are You Up For the Challenge: 700 Level Questions
A. 20, 60, 40
B. 24, 40, 30
C. 10, 90, 20
D. 12, 90, 18
E. 24, 80, 36
Are You Up For the Challenge: 700 Level Questions
05 May 2022, 11:03
Kudos
Bookmarks
To save time, I will focus on solving for C only.
It takes C twice as long as A and B together to do a certain work: \(C = 2(A + B)\)
\(\frac{C}{2}= A+B\)
We are also told that the three men complete the work together in 10 days: \(\frac{1}{A}+\frac{1}{B}+\frac{1}{C}=\frac{1}{10}\)
Substituting in A+B = C/2 into the above:
\(\frac{1}{\frac{C}{2}}+\frac{1}{C}=\frac{1}{10}\)
\(\frac{2}{C}+\frac{1}{C}=\frac{1}{10}\)
\(\frac{3}{C}=\frac{1}{10}\)
\(C = 30\)
Answer B
It takes C twice as long as A and B together to do a certain work: \(C = 2(A + B)\)
\(\frac{C}{2}= A+B\)
We are also told that the three men complete the work together in 10 days: \(\frac{1}{A}+\frac{1}{B}+\frac{1}{C}=\frac{1}{10}\)
Substituting in A+B = C/2 into the above:
\(\frac{1}{\frac{C}{2}}+\frac{1}{C}=\frac{1}{10}\)
\(\frac{2}{C}+\frac{1}{C}=\frac{1}{10}\)
\(\frac{3}{C}=\frac{1}{10}\)
\(C = 30\)
Answer B
05 May 2022, 14:58
Kudos
Bookmarks
Bunuel
B would take three times as long as A and C together.
Time and rate have a reciprocal relationship.
Since the time ratio for B and A+C = 3:1, the rate ratio for B and A+C = 1:3.
Let the job = 40 widgets.
The three men complete the work together in 10 days.
Since A+B+C take 10 days to produce the 40-widget job, the combined rate for A+B+C \(= \frac{work}{time} = \frac{40}{10} = 4\) widgets per day.
Since the rate ratio for B and A+C = 1:3, the rate for B = 1 widget per day, while the rate for A+C = 3 widgets per day, for a combined rate of 4 widgets per day.
B's rate of 1 widget per day implies that B's time to produce the 40-widget job \(= \frac{work}{rate} = \frac{40}{1} = 40\) days.
If we assume that the times in the answer choices are for A, B and C in that order -- something the prompt should make clear -- only one option indicates a time of 40 hours for B.
