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

 It is currently 25 Jan 2020, 18:33

### 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 500-gallon cistern is filled to half its capacity with water. At wha

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 60647
A 500-gallon cistern is filled to half its capacity with water. At wha  [#permalink]

### Show Tags

28 Mar 2018, 23:41
00:00

Difficulty:

5% (low)

Question Stats:

87% (00:59) correct 13% (01:48) wrong based on 65 sessions

### HideShow timer Statistics

A 500-gallon cistern is filled to half its capacity with water. At what rate, in gallons per minute, is the amount of water in the cistern increasing if both the inlet pipe and outlet pipe are open?

(1) The inlet pipe pumps water into the cistern at a rate of 7 gallons per 30 seconds.
(2) The outlet pipe pumps water out of the cistern at the rate of 12 gallons every 1 minute 30 seconds.

_________________
Manager
Joined: 15 Nov 2017
Posts: 169
Location: India
Concentration: Operations, Marketing
GPA: 4
WE: Operations (Retail)
A 500-gallon cistern is filled to half its capacity with water. At wha  [#permalink]

### Show Tags

Updated on: 29 Mar 2018, 05:38
Bunuel wrote:
A 500-gallon cistern is filled to half its capacity with water. At what rate, in gallons per minute, is the amount of water in the cistern increasing if both the inlet pipe and outlet pipe are open?

(1) The inlet pipe pumps water into the cistern at a rate of 7 gallons per 30 seconds.
(2) The outlet pipe pumps water out of the cistern at the rate of 12 gallons every 1 minute 30 seconds.

Since the Q. asks for the rate of water increase- we must know the inlet and outlet rates
1. Provides the inlet rate- nothing can be said whether the amount of water in the cistern would increase or decrease untill we know about the outlet rate
2. Provides the outlet rate- nothing can be said whether the amount of water in the cistern would increase or decrease untill we know about the inlet rate

Combining both would give us the answer(till now we do not know whether the increase would be positive or negative, but it is sure that we will get the answer)
{For those who still seek the answer,
Inlet rate- 14 gallons/min.
Outlet rate - 12/1.5 (1.5 is 3/2)
- 12*2/3 = 8 gallons/min.
Diff. - 6 gallons/min is the rate of increase}

Ans. C
_________________

Originally posted by aggvipul on 28 Mar 2018, 23:54.
Last edited by aggvipul on 29 Mar 2018, 05:38, edited 1 time in total.
examPAL Representative
Joined: 07 Dec 2017
Posts: 1155
Re: A 500-gallon cistern is filled to half its capacity with water. At wha  [#permalink]

### Show Tags

29 Mar 2018, 00:10
Bunuel wrote:
A 500-gallon cistern is filled to half its capacity with water. At what rate, in gallons per minute, is the amount of water in the cistern increasing if both the inlet pipe and outlet pipe are open?

(1) The inlet pipe pumps water into the cistern at a rate of 7 gallons per 30 seconds.
(2) The outlet pipe pumps water out of the cistern at the rate of 12 gallons every 1 minute 30 seconds.

To find the total rate, we'll need to know the rate of both the outlet and the inlet pipe or the change in volume over time.
We'll look for statements that give us this information, a Logical approach.

(1) what of the outlet pipe?
Insufficient.

(2) what of the inlet pipe?
Insufficient.

Combined:
We know have both the input rate and the output rate and can calculate the total rate of change of water in the cistern.
Sufficient.

_________________
Retired Moderator
Joined: 27 Oct 2017
Posts: 1398
Location: India
GPA: 3.64
WE: Business Development (Energy and Utilities)
Re: A 500-gallon cistern is filled to half its capacity with water. At wha  [#permalink]

### Show Tags

29 Mar 2018, 00:43
Hiii

Perfect approach to the Data sufficiency questions.
There is no need to solve for the values.
We just need to judge whether we can solve it or not using only the information provide vide the statement s and question stem.

[quite="DavidTutorexamPAL"]
Bunuel wrote:
A 500-gallon cistern is filled to half its capacity with water. At what rate, in gallons per minute, is the amount of water in the cistern increasing if both the inlet pipe and outlet pipe are open?

(1) The inlet pipe pumps water into the cistern at a rate of 7 gallons per 30 seconds.
(2) The outlet pipe pumps water out of the cistern at the rate of 12 gallons every 1 minute 30 seconds.

To find the total rate, we'll need to know the rate of both the outlet and the inlet pipe or the change in volume over time.
We'll look for statements that give us this information, a Logical approach.

(1) what of the outlet pipe?
Insufficient.

(2) what of the inlet pipe?
Insufficient.

Combined:
We know have both the input rate and the output rate and can calculate the total rate of change of water in the cistern.
Sufficient.

_________________
Re: A 500-gallon cistern is filled to half its capacity with water. At wha   [#permalink] 29 Mar 2018, 00:43
Display posts from previous: Sort by