Find all School-related info fast with the new School-Specific MBA Forum

It is currently 21 Nov 2014, 12:40

Close

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
Your Progress

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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Jamal can fill the vending machine in 45 minutes. When his

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Intern
Intern
User avatar
Joined: 19 Mar 2012
Posts: 2
Location: United States
GMAT Date: 04-17-2012
Followers: 0

Kudos [?]: 5 [0], given: 0

Jamal can fill the vending machine in 45 minutes. When his [#permalink] New post 19 Mar 2012, 10:38
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

100% (01:48) correct 0% (00:00) wrong based on 7 sessions
Hi,

I have this problem I'm trying to figure out:

Jamal can fill the vending machine in 45 minutes. When his sister, Violet, helps him, it takes them 20 minutes. How long would it take Violet to fill the machine by herself?

The solution formula the textbook provides is:

20/x + 20/45 = 1

This is confusing to me, because shouldn't the logic of it work like this:

Work by Jamal/Total Work by both + Work by Violet (x)/ Work by both = 1

, or 45/20 + x/20 = 1?

P.S. I know that often they recommend to break down work rate to a unit of time. So, in Jamal's case it would be 1/45, and total rate would be 1/20. So, in that case 1/45:1/20, actually, would mean 20/45. But is 1/45:1/20 + x:1/20 = 1? Isn't 1 a 100%, and in this case 1 is what?? I'm confused :shock:

Thank you for any help whatsoever.
Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 23989
Followers: 3722

Kudos [?]: 30952 [0], given: 3265

Re: Jamal can fill the vending machine in 45 minutes. When his [#permalink] New post 19 Mar 2012, 11:13
Expert's post
EugeneZelenyi wrote:
Hi,

I have this problem I'm trying to figure out:

Jamal can fill the vending machine in 45 minutes. When his sister, Violet, helps him, it takes them 20 minutes. How long would it take Violet to fill the machine by herself?

The solution formula the textbook provides is:

20/x + 20/45 = 1

This is confusing to me, because shouldn't the logic of it work like this:

Work by Jamal/Total Work by both + Work by Violet (x)/ Work by both = 1

, or 45/20 + x/20 = 1?

P.S. I know that often they recommend to break down work rate to a unit of time. So, in Jamal's case it would be 1/45, and total rate would be 1/20. So, in that case 1/45:1/20, actually, would mean 20/45. But is 1/45:1/20 + x:1/20 = 1? Isn't 1 a 100%, and in this case 1 is what?? I'm confused :shock:

Thank you for any help whatsoever.


Welcome to GMAT Club. Below is a solution for your question.

Jamal can fill the vending machine in 45 minutes. When his sister, Violet, helps him, it takes them 20 minutes. How long would it take Violet to fill the machine by herself?

Say Violet needs x minute to fill the machine by herself, so her rate is 1/x job/minute. Since Jamal can fill the vending machine in 45 minutes then his rate is 1/45 job/minute. Their combined rate would be 1/x+1/45, which as we are told equal to 1/20 job/minute, so 1/x+1/45=1/20 --> x=36 minute.

Generally for multiple entities: \frac{1}{t_1}+\frac{1}{t_2}+\frac{1}{t_3}+...+\frac{1}{t_n}=\frac{1}{T}, where T is time needed for these entities to complete a given job working simultaneously.

Check this for more on this subject: two-consultants-can-type-up-a-report-126155.html#p1030079

Hope it helps.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

COLLECTION OF QUESTIONS:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS ; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
25 extra-hard Quant Tests

Take a Survey about GMAT Prep - Win Prizes!

Intern
Intern
User avatar
Joined: 19 Mar 2012
Posts: 2
Location: United States
GMAT Date: 04-17-2012
Followers: 0

Kudos [?]: 5 [0], given: 0

Re: Jamal can fill the vending machine in 45 minutes. When his [#permalink] New post 19 Mar 2012, 11:33
It does help! Thank you very much.
Re: Jamal can fill the vending machine in 45 minutes. When his   [#permalink] 19 Mar 2012, 11:33
    Similar topics Author Replies Last post
Similar
Topics:
22 Tap A can fill a tank in 36 minutes, Tap B can fill the same conty911 8 27 Sep 2012, 09:21
7 Machine A can fill an order of widgets in a hours. Machine B nshang 2 17 Sep 2011, 01:36
In a certain canned food company, machine A can fill 48 cans vcbabu 1 22 Jul 2009, 11:28
Pump one can fill tank to 1/3 capacity in 45 minutes Pump 2 jamesrwrightiii 1 26 Aug 2007, 05:24
Valve A can fulfill 1/3 of a container in 45 minutes, B can johnycute 3 30 Dec 2006, 11:57
Display posts from previous: Sort by

Jamal can fill the vending machine in 45 minutes. When his

  Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.