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.
Jun 2106:30 AM PDT
-08:30 AM PDT
Not only the typical inference questions but also all other CR questions on the GMAT require the ability to deduce from the given information. Come master how to draw inferences accurately and efficiently with Verbal Expert-Sunita Singhvi. Limited Seats!
Jun 2111:00 AM IST
-01:00 PM IST
Do RC/MSR passages scare you? e-GMAT is conducting a masterclass to help you learn – Learn effective reading strategies Tackle difficult RC & MSR with confidence Excel in timed test environment
Jun 2211:30 AM EDT
-12:30 PM EDT
Learn how Keshav, a Chartered Accountant, scored an impressive 705 on GMAT in just 30 days with GMATWhiz's expert guidance. In this video, he shares preparation tips and strategies that worked for him, including the mock, time management, and more.
Jun 2308:00 PM PDT
-09:00 PM PDT
Full-length FE mock with insightful analytics, weakness diagnosis, and video explanations!
Jun 3008:00 AM PDT
-11:59 PM PDT
Join us June 30th for 2 weeks of GMAT questions (just 8 per day) to help with your prep and to compete with your fellow GMAT Clubbers for a chance to win a prize fund of $30,000 for you and your team-mates!
16 Sep 2014, 01:31
Kudos
Bookmarks
B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
55%
(hard)
Question Stats:
63% (01:54) correct
37%
(01:51)
wrong
based on 405
sessions
History
Date
Time
Result
Not Attempted Yet
Machine A and B working together at their constant rates can complete a certain task in 6 days. In how many days, working alone, can machine A complete the task?
(1) The average (arithmetic mean) of the respective times A and B would each take to complete the task working alone is 12.5 days.
(2) It would take machine A 5 more days to complete the task alone than it would take machine B to complete the task.
(1) The average (arithmetic mean) of the respective times A and B would each take to complete the task working alone is 12.5 days.
(2) It would take machine A 5 more days to complete the task alone than it would take machine B to complete the task.
16 Sep 2014, 01:31
Kudos
Bookmarks
Official Solution:
Machine A and B working together at their constant rates can complete a certain task in 6 days. In how many days, working alone, can machine A complete the task?
Let A and B be the times needed for machines A and B to complete the task working alone, respectively. Thus, we have \(\frac{1}{A}+\frac{1}{B}=\frac{1}{6}\).
(1) The average (arithmetic mean) of the respective times A and B would each take to complete the task working alone is 12.5 days.
This implies that \(A+B=2*12.5=25\). However, since we do not know which machine is faster (we cannot differentiate between A and B), even if we substitute B with \(25-A\) into \(\frac{1}{A}+\frac{1}{B}=\frac{1}{6}\) to get \(\frac{1}{A} + \frac{1}{25-A} = \frac{1}{6}\) and solve, we must get two different answers for A and B: \(A \lt B\) and \(A \gt B\). Not sufficient.
(2) It would take machine A 5 more days to complete the task alone than it would take machine B to complete the task.
This implies that \(A=B+5\). Substituting this into the equation, we get \(\frac{1}{A}+\frac{1}{A-5}=\frac{1}{6}\). We can solve for \(A\) to get \(A=2\) or \(A=15\). However, \(A=2\) cannot be true since it would make \(B\) negative, so \(A = 15\) is the only valid solution. Sufficient.
Answer: B
Machine A and B working together at their constant rates can complete a certain task in 6 days. In how many days, working alone, can machine A complete the task?
Let A and B be the times needed for machines A and B to complete the task working alone, respectively. Thus, we have \(\frac{1}{A}+\frac{1}{B}=\frac{1}{6}\).
(1) The average (arithmetic mean) of the respective times A and B would each take to complete the task working alone is 12.5 days.
This implies that \(A+B=2*12.5=25\). However, since we do not know which machine is faster (we cannot differentiate between A and B), even if we substitute B with \(25-A\) into \(\frac{1}{A}+\frac{1}{B}=\frac{1}{6}\) to get \(\frac{1}{A} + \frac{1}{25-A} = \frac{1}{6}\) and solve, we must get two different answers for A and B: \(A \lt B\) and \(A \gt B\). Not sufficient.
(2) It would take machine A 5 more days to complete the task alone than it would take machine B to complete the task.
This implies that \(A=B+5\). Substituting this into the equation, we get \(\frac{1}{A}+\frac{1}{A-5}=\frac{1}{6}\). We can solve for \(A\) to get \(A=2\) or \(A=15\). However, \(A=2\) cannot be true since it would make \(B\) negative, so \(A = 15\) is the only valid solution. Sufficient.
Answer: B
General Discussion
Nightmare007
Joined: 26 Aug 2016
Last visit: 05 Aug 2020
Posts: 438
Own Kudos:
Given Kudos: 204
Location: India
Concentration: Operations, International Business
Schools: ISB '20 (M) Simon '21 (WL)
GMAT 1: 690 Q50 V33
GMAT 2: 700 Q50 V33
GMAT 3: 730 Q51 V38
GPA: 4
WE:Information Technology (Consulting)
Products:
22 May 2018, 22:16
Kudos
Bookmarks
Hi Bunuel,
Can you spot my error
(A+B)/AB = 1/6.
Statement 1 : A + B = 25
AB = 150.
A-B = ((A+B)^2 - 4AB)^1/2
A-B = constant.
A+B = 25
Can't we get statement 1 enough.
???
Can you spot my error
(A+B)/AB = 1/6.
Statement 1 : A + B = 25
AB = 150.
A-B = ((A+B)^2 - 4AB)^1/2
A-B = constant.
A+B = 25
Can't we get statement 1 enough.
???
