Working alone, pump A can empty a pool in 3 hours. Working alone, pump B can empty the same pool in 2 hours. Working together, how how many minutes will it take pump A and pump B to empty the pool?
(A) 72
(B) 75
(C) 84
(D) 96
(E) 108
The OA is A.
I'm confused with this PS question. Experts, any suggestion? I don't know how can I solve it. Thanks in advance.
5-Day Free Trial
5-day free, full-access trial TTP
Available with Beat the GMAT members only code
MORE DETAILS
Working alone, pump A can empty a pool in 3 hours...
This topic has expert replies
-
BTGmoderatorLU
- Moderator
- Posts: 2209
- Joined: Sun Oct 15, 2017 1:50 pm
- Followed by:6 members
-
EconomistGMATTutor
- GMAT Instructor
- Posts: 555
- Joined: Wed Oct 04, 2017 4:18 pm
- Thanked: 180 times
- Followed by:12 members
Hello LUANDATO.
Let's take a look at your question.
Working alone, pump A can empty a pool in 3 hours, it implies that pump A wor at a rate 1/3 pool/hour.
Working alone, pump B can empty a pool in 2 hours, it implies that pump A wor at a rate 1/2 pool/hour.
Working together the rate will be equal to $$\frac{1}{3}+\frac{1}{2}=\frac{5}{6}\ \text{pool per hour}$$. Now we have the following: $$\frac{5\ }{6\ }\ \frac{pool}{60\ \min}=1\ \frac{pool}{x}\ \Leftrightarrow\ x=72\ \min.$$ This is why the correct answer is the option [spoiler]A=72[/spoiler].
I hope this answer may help you.
I'm available if you'd like a follow-up.
Regards.
Let's take a look at your question.
Working alone, pump A can empty a pool in 3 hours, it implies that pump A wor at a rate 1/3 pool/hour.
Working alone, pump B can empty a pool in 2 hours, it implies that pump A wor at a rate 1/2 pool/hour.
Working together the rate will be equal to $$\frac{1}{3}+\frac{1}{2}=\frac{5}{6}\ \text{pool per hour}$$. Now we have the following: $$\frac{5\ }{6\ }\ \frac{pool}{60\ \min}=1\ \frac{pool}{x}\ \Leftrightarrow\ x=72\ \min.$$ This is why the correct answer is the option [spoiler]A=72[/spoiler].
I hope this answer may help you.
I'm available if you'd like a follow-up.
Regards.
GMAT Prep From The Economist
We offer 70+ point score improvement money back guarantee.
Our average student improves 98 points.
We offer 70+ point score improvement money back guarantee.
Our average student improves 98 points.
GMAT/MBA Expert
-
Scott@TargetTestPrep
- GMAT Instructor
- Posts: 7249
- Joined: Sat Apr 25, 2015 10:56 am
- Location: Los Angeles, CA
- Thanked: 43 times
- Followed by:29 members
The combined rate of pumps A and B is:BTGmoderatorLU wrote:Working alone, pump A can empty a pool in 3 hours. Working alone, pump B can empty the same pool in 2 hours. Working together, how how many minutes will it take pump A and pump B to empty the pool?
(A) 72
(B) 75
(C) 84
(D) 96
(E) 108
1/3 + 1/2 = 2/6 + 3/6 = 5/6, so the time is 1/(5/6) = 6/5 hours, which is 6/5 x 60 = 72 minutes.
Answer: A
Scott Woodbury-Stewart
Founder and CEO
[email protected]
See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews
