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 2308:00 PM PDT
-09:00 PM PDT
Video explanations + diagnosis of 10 weakest areas + 150+ short videos + study plan!
Apr 2301:30 AM EDT
-02:30 AM EDT
Struggling with GMAT Verbal as a non-native speaker? Harsh improved his score from 595 to 695 in just 45 days—and scored a 99 %ile in Verbal (V88)! Learn how smart strategy, clarity, and guided prep helped him gain 100 points.
Apr 2512:30 AM EDT
-01:30 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.
Apr 2610:00 AM EDT
-11:00 AM EDT
The Target Test Prep course represents a quantum leap forward in GMAT preparation, a radical reinterpretation of the way that students should study. Try before you buy with a 5-day, full-access trial of the course for FREE!
Apr 2711:00 AM EDT
-12:00 PM EDT
Prefer video-based learning? The Target Test Prep OnDemand course is a one-of-a-kind video masterclass featuring 400 hours of lecture-style teaching by Scott Woodbury-Stewart, founder of Target Test Prep and one of the most accomplished GMAT instructors
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.
C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
5%
(low)
Question Stats:
88% (01:41) correct
12%
(02:14)
wrong
based on 202
sessions
History
Date
Time
Result
Not Attempted Yet
A chemical lab is scheduled to go through two air ventillation systems, a basic system and a more advanced system that takes half an hour and two hours respectively to fully ventillate the room. If both ventillation systems were to operate at the same time with thier respective constant rates, how many hours would it take to fully ventilate the chemical lab?
(A) 1/4
(B) 1/3
(C) 2/5
(D) 5/4
(E) 3/2
(A) 1/4
(B) 1/3
(C) 2/5
(D) 5/4
(E) 3/2
10 Sep 2013, 18:30
Kudos
Bookmarks
amgelcer
I'm happy to respond.
As I discuss in this post,
https://magoosh.com/gmat/2012/gmat-work-rate-problems/
always add rates when machines work together.
basic system = A --- ventilates in 0.5 hr, so A's rate is (1 room)/(0.5 hour) = 2
more advanced system = B --- ventilates in 2 hr, so A's rate is (1 room)/(2 hour) = 0.5
Add rate --- combined rate = 2 + 0.5 = 2.5 rooms/hour = 5/2 rooms/hour
Now, how long would it take for a combo, ventilating at 5/2 rooms/hour, to ventilate a single room? We use the "ART" equation ----
A = RT --- that is, (amount) = (rate)*(time)
(1 room) = (5/2 rooms/hour)*T
1 = (5/2)*T
2/5 = T
So, the combo takes 2/5 of an hour to ventilate a room. Answer = (C)
Does this make sense?
Mike
11 Sep 2013, 00:13
Kudos
Bookmarks
If you had to guess on this question, there are some ways to logically knock out a bunch of answers.
The two ventilation systems can clear the room in 1/2 hour and 2 hours, so combined they have to take less than 1/2 hour to do the job. Answers D and E are too big. Also, if both machines could do the job in 1/2 hour, then it would take 1/4 hour combined. Since the second machine takes 2 hours (and not 1/2 hour), then answer A is too small.
t1000
The two ventilation systems can clear the room in 1/2 hour and 2 hours, so combined they have to take less than 1/2 hour to do the job. Answers D and E are too big. Also, if both machines could do the job in 1/2 hour, then it would take 1/4 hour combined. Since the second machine takes 2 hours (and not 1/2 hour), then answer A is too small.
t1000
