GMAT Question of the Day: Daily via email | Daily via Instagram New to GMAT Club? Watch this Video

 It is currently 03 Jun 2020, 21:20

### 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

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# A tank is fitted with pipes, some filling it and the rest draining it.

Author Message
TAGS:

### Hide Tags

MBA Section Director
Affiliations: GMAT Club
Joined: 21 Feb 2012
Posts: 7611
City: Pune
A tank is fitted with pipes, some filling it and the rest draining it.  [#permalink]

### Show Tags

31 Jul 2019, 23:02
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 100% (03:06) wrong based on 4 sessions

### HideShow timer Statistics

Official CAT 2018 Questions; Section: QA

A tank is fitted with pipes, some filling it and the rest draining it. All filling pipes fill at the same rate, and all draining pipes drain at the same rate. The empty tank gets completely filled in 6 hours when 6 filling and 5 draining pipes are on, but this time becomes 60 hours when 5 filling and 6 draining pipes are on. In how many hours will the empty tank get completely filled when one draining and two filling pipes are on?

Spoiler: :: OA
10

_________________
MBA Spotlight - GMAT Club's Top 20 MBA Fair.
2020 MBA Applicants: Introduce Yourself Here!
SVP
Joined: 24 Jul 2011
Posts: 2052
GMAT 1: 780 Q51 V48
GRE 1: Q800 V740
Re: A tank is fitted with pipes, some filling it and the rest draining it.  [#permalink]

### Show Tags

03 Aug 2019, 02:43
Top Contributor
Narenn wrote:
Official CAT 2018 Questions; Section: QA

A tank is fitted with pipes, some filling it and the rest draining it. All filling pipes fill at the same rate, and all draining pipes drain at the same rate. The empty tank gets completely filled in 6 hours when 6 filling and 5 draining pipes are on, but this time becomes 60 hours when 5 filling and 6 draining pipes are on. In how many hours will the empty tank get completely filled when one draining and two filling pipes are on?

Spoiler: :: OA
10

If x=efficiency of input pipe and y=efficiency of output pipe, then
36x-30y=1
300x-360y=1
t*2x-t*y=1
=> x= 1/12, and y=1/15

Thus, time taken when one draining and two filling pipes are on = t = 1/(2x-y) = 1/(1/6-1/15) = 10 hours.
_________________

Awesome Work | Honest Advise | Outstanding Results

Reach Out, Lets chat!
Email: info at gyanone dot com | +91 98998 31738 | Skype: gyanone.services
SVP
Joined: 24 Jul 2011
Posts: 2052
GMAT 1: 780 Q51 V48
GRE 1: Q800 V740
A tank is fitted with pipes, some filling it and the rest draining it.  [#permalink]

### Show Tags

07 Aug 2019, 01:33
Top Contributor
Alternative approach:
If x = rate of input and y = rate of output [original].
Then:
(x-y) = 10*(5x/6 - 6y/5) [as the time taken is 10 times in the second case, so the rate in the first case must be 10 times the second]
=> y =(2/3)x

Put this in 6*(x-y)=1, to get x=1/2 and y=1/3

Then to find the required time t, we solve t*(x/3 - y/5) = 1, to get t=10 hours.
_________________

Awesome Work | Honest Advise | Outstanding Results

Reach Out, Lets chat!
Email: info at gyanone dot com | +91 98998 31738 | Skype: gyanone.services
A tank is fitted with pipes, some filling it and the rest draining it.   [#permalink] 07 Aug 2019, 01:33

# A tank is fitted with pipes, some filling it and the rest draining it.

Moderator: cfc198