Check GMAT Club Decision Tracker for the Latest School Decision Releases https://gmatclub.com/AppTrack

 It is currently 24 May 2017, 21:10

### 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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# A constructor is using three water filling pumps, X,Y, and Z

Author Message
TAGS:

### Hide Tags

Intern
Joined: 27 Sep 2010
Posts: 27
Followers: 1

Kudos [?]: 80 [0], given: 3

A constructor is using three water filling pumps, X,Y, and Z [#permalink]

### Show Tags

23 Jan 2011, 02:54
00:00

Difficulty:

(N/A)

Question Stats:

100% (02:06) correct 0% (00:00) wrong based on 26 sessions

### HideShow timer Statistics

A constructor is using three water filling pumps, X,Y, and Z, working together at their respective constant rates to fill an initially empty tank in 9 hours.Pumps X and Y,working together at their respective constant rates can fill the same tank in 10 hours.How many hours will pump Z, working alone at its constant rate, take to fill the same tank?

[Reveal] Spoiler:
90

(i don't have the answer choices for the question above.)

Last edited by MichelleSavina on 23 Jan 2011, 06:49, edited 1 time in total.
Intern
Joined: 05 Nov 2010
Posts: 1
Followers: 0

Kudos [?]: 0 [0], given: 0

Re: Three water filling pumps, X,Y, and Z, working together [#permalink]

### Show Tags

23 Jan 2011, 03:55
Let A be total work,

Given 1). A/(X+Y+Z)=9
Given 2). A/(X+Y)=10

Question is A/Z = ?

From given 1) and 2), we know that 9(X+Y+Z)=10(X+Y), therefore 9Z=(X+Y)=A/10

A/Z = 90
Math Expert
Joined: 02 Sep 2009
Posts: 38858
Followers: 7728

Kudos [?]: 106061 [2] , given: 11607

Re: Three water filling pumps, X,Y, and Z, working together [#permalink]

### Show Tags

23 Jan 2011, 04:03
2
KUDOS
Expert's post
MichelleSavina wrote:
Q) A constructor is using three water filling pumps, X,Y, and Z, working together at their respective constant rates to fill an initially empty tank in 9 hours. Pumps X and Y,working together at their respective constant rates can fill the same tank in 10 hours. How many hours will pump Z, working alone at its constant rate, take to fill the same tank?

A) 90

Let the times needed for the pumps X, Y, and Z, working ALONE at their respective constant rates to fill the empty tank be x, y and z respectively.

Given: $$\frac{1}{x}+\frac{1}{y}+\frac{1}{z}=\frac{1}{9}$$ (remember we can add the rates) and $$\frac{1}{x}+\frac{1}{y}=\frac{1}{10}$$.

Subtract 2 from 1: $$\frac{1}{z}=\frac{1}{9}-\frac{1}{10}=\frac{1}{90}$$ --> $$z=90$$.

Or: you can notice that as all 3 pumps can fill the empty tank in 9 hours and only X and Y can fill the tank in 10 hours, so they need 1 more hour, then Z is doing in 9 hours the work done by X and Y in this 1 extra hour, so as X and Y need total of 10 hours to fill the empty tank then Z alone will need 9*10=90 hours to fill the empty tank alone.

Several important things you should know to solve work problems with examples:
word-translations-rates-work-104208.html#p812628
_________________
GMAT Club Legend
Joined: 09 Sep 2013
Posts: 15431
Followers: 649

Kudos [?]: 207 [0], given: 0

Re: A constructor is using three water filling pumps, X,Y, and Z [#permalink]

### Show Tags

14 Feb 2017, 00:31
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
Re: A constructor is using three water filling pumps, X,Y, and Z   [#permalink] 14 Feb 2017, 00:31
Similar topics Replies Last post
Similar
Topics:
3 Two different pumps are used to fill an empty water tank. The first pu 3 22 May 2017, 18:28
19 There are three different hoses used to fill a pool: hose 11 08 Dec 2016, 13:06
13 A small water pump would take 2 hours to fill an empty tank 8 30 Dec 2015, 11:16
12 One water pump can fill half of a certain empty tank in 3 hours. Anoth 9 02 Feb 2017, 12:07
11 A pump started filling an empty pool with water and continue 11 21 Mar 2017, 06:22
Display posts from previous: Sort by