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.
Apr 2912:30 AM EDT
-01:30 AM EDT
Learn how Kamakshi achieved a GMAT 675 with an impressive 96th %ile in Data Insights. Discover the unique methods and exam strategies that helped her excel in DI along with other sections for a balanced and high score.
Apr 3001:30 AM EDT
-02:30 AM EDT
At one point, she believed GMAT wasn’t for her. After scoring 595, self-doubt crept in and she questioned her potential. But instead of quitting, she made the right strategic changes. The result? A remarkable comeback to 695. Check out how Saakshi did it.
May 0111:00 AM PDT
-12:00 PM PDT
Free- full-length test + 15 concept videos + 150+ short videos + study plan!
May 0306:30 AM PDT
-08:30 AM PDT
Verbal trouble on GMAT? Fix it NOW! Join Sunita Singhvi for a focused webinar on actionable strategies to boost your Verbal score and take your performance to the next level.
30 Mar 2012, 13:29
Kudos
Bookmarks
D
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% (01:21) correct
18%
(01:31)
wrong
based on 275
sessions
History
Date
Time
Result
Not Attempted Yet
A worker can load 1 full truck in 6 hours. A second worker can load the same truck in 7 hours. If both workers load one truck simultaneously while maintaining their constant rates, approximately how long, in hours, will it take them to fill 1 truck?
A. 0.15
B. 0.31
C. 2.47
D. 3.23
E. 3.25
The site where I pulled this question states that the answer is E. 3.25. I'm convinced that 3hr 3/13 minutes is closer to E. 3.23. Who is correct? Their reasoning which I think must contain an error: At this point, we may not be able to decide between (D) or (E). However, the decimal is important. Because the denominator is 13, we know the decimal cannot equal .25. We can also see that 3/12 will yield .25, so 3/13 will be slightly lower. Choice (E).
A. 0.15
B. 0.31
C. 2.47
D. 3.23
E. 3.25
The site where I pulled this question states that the answer is E. 3.25. I'm convinced that 3hr 3/13 minutes is closer to E. 3.23. Who is correct? Their reasoning which I think must contain an error: At this point, we may not be able to decide between (D) or (E). However, the decimal is important. Because the denominator is 13, we know the decimal cannot equal .25. We can also see that 3/12 will yield .25, so 3/13 will be slightly lower. Choice (E).
30 Mar 2012, 14:58
Kudos
Bookmarks
ralanko
You are right, answer should be D, not E.
Remember we can add the rates of individual entities to get the combined rate.
Generally for multiple entities: \(\frac{1}{t_1}+\frac{1}{t_2}+\frac{1}{t_3}+...+\frac{1}{t_n}=\frac{1}{T}\), where \(T\) is time needed for these entities to complete a given job working simultaneously and \(t_1\), \(t_2\), ..., \(t_n\) are individual times needed for them to complete the job alone.
So for two pumps, workers, etc. we'll have \(\frac{1}{t_1}+\frac{1}{t_2}=\frac{1}{T}\) --> \(T=\frac{t_1*t_2}{t_1+t_2}\) (general formula for 2 workers, pumps, ...).
Back to the original problem: for two outlets the formula becomes: \(\frac{1}{6}+\frac{1}{7}=\frac{1}{T}\) --> \(\frac{13}{42}=\frac{1}{T}\) --> \(T=\frac{42}{13}\approx{3.23}\) (or directly \(T=\frac{t_1*t_2}{t_1+t_2}=\frac{6*7}{6+7}=\frac{42}{13}\approx{3.23}\)).
Answer: D.
Check this for more on this subject: two-consultants-can-type-up-a-report-126155.html#p1030079
Hope it helps.
P.S. Please post PS questions in the PS subforum: gmat-problem-solving-ps-140/ and DS questions in the DS subforum: gmat-data-sufficiency-ds-141/
No posting of PS/DS questions is allowed in the main Math forum.
20 Feb 2018, 17:17
Kudos
Bookmarks
ralanko
One approach is to assign a nice value to the entire job (of filling a truck)
We want a number that works well with the given times (6 hours and 7 hours)
42 is such a number.
So, let's say that filling the truck is equivalent to shoveling 42 scoops of dirt into it.
A worker (we'll call worker A) can load 1 full truck in 6 hours
Rate = output/time = 42 scoops/6 hours = 7 scoops/hour
So, worker A's RATE is 7 scoops/hour
Worker B) can load 1 full truck in 7 hours
Rate = output/time = 42 scoops/7 hours = 6 scoops/hour
So, worker B's RATE is 6 scoops/hour
So, their COMBINED rate = 7 scoops/hour + 6 scoops/hour
= 13 scoops/hour
Worker B) Approximately how long, in hours, will it take them to fill 1 truck?
Time = output/rate
= 42 scoops/13 scoops/hour
= 42/13 hours
= 3 3/13 hours
ASIDE: Notice that 3 3/12 hours = 3.25 hours
So, 3 3/13 hours will equal a little less than 3.25 hours
Answer: D
Cheers,
Brent
