Find all School-related info fast with the new School-Specific MBA Forum
Learn more about the recent changes... close

It is currently 22 May 2013, 22:01
Customize  |  Hide

Search
Register
New posts
Unanswered

M11 #19

  Question banks Downloads My Bookmarks Reviews  
  Oldest Best Reply
Search for:
 
Print view
First unread post
Author Message
1 KUDOS received
Senior Manager
Senior Manager
Joined: 16 Jul 2009
Posts: 273
Followers: 2

Kudos [?]: 16 [1] , given: 3

GMAT Tests User
M11 #19 [#permalink] New post 19 May 2010, 08:41
1
This post received
KUDOS
Working at their normal rates, 20 diggers can dig a 100-meter long trench in hard soil in 3 days. A construction company ordered the diggers to dig a 180-meter long trench in soft soil. If diggers can work 20% faster in soft soil than in hard soil, how many diggers are required to complete this task in 3 days?

25
28
29
30
32

It follows from the stem that in 3 days one digger can dig 5 meters of trench in hard soil. Therefore, his digging speed on hard soil is \frac{5}{3} meters per day. On soft soil his speed would be \frac{5}{3}*\frac{6}{5}= \frac{6}{3} meters per day or 6 meters in 3 days. If one digger can dig 6 meters of a trench in 3 days then we need \frac{180}{3} = 30 diggers to dig the entire 180-meter long trench in 3 days.

Here how do we arrive at the fraction \frac{6}{5}?
1 KUDOS received
Manager
Manager
Joined: 08 May 2010
Posts: 144
Followers: 0

Kudos [?]: 49 [1] , given: 39

GMAT ToolKit User
Re: M11 #19 [#permalink] New post 19 May 2010, 08:49
1
This post received
KUDOS
I would do the problem in a different way. The 20 diggers dig 100 meters in 3 days in hard soil. They then dig 20% faster in soft soil. So this should be 120 meters in 3 days. Now I set up a proportion 120meters for 20 diggers compared with 180 meters for how many workers? The days and soil are now the same. Cross multiplying I get 20(180) = 120x ==> x= 20(180)/120, x= 30.

I don't know whether this is correct but it seems to make sense.
If this has been helpful to you please give kudos.
Thanks
Skip
Senior Manager
Senior Manager
Joined: 16 Jul 2009
Posts: 273
Followers: 2

Kudos [?]: 16 [0], given: 3

GMAT Tests User
Re: M11 #19 [#permalink] New post 19 May 2010, 23:51
Amazing one Skip! You've indeed skipped..:) all the steps given in the solution and made it a under 1-minute solution..Kudos for you..
CIO
CIO
Joined: 02 Oct 2007
Posts: 1261
Followers: 75

Kudos [?]: 506 [0], given: 334

GMAT ToolKit User GMAT Tests User
Re: M11 #19 [#permalink] New post 20 May 2010, 00:05
\frac{6}{5} is 1.2, which comes from "20% faster in soft soil". \frac{5}{3}*\frac{6}{5} is the same as \frac{5}{3}*1.2
abhi758 wrote:
Working at their normal rates, 20 diggers can dig a 100-meter long trench in hard soil in 3 days. A construction company ordered the diggers to dig a 180-meter long trench in soft soil. If diggers can work 20% faster in soft soil than in hard soil, how many diggers are required to complete this task in 3 days?

25
28
29
30
32

It follows from the stem that in 3 days one digger can dig 5 meters of trench in hard soil. Therefore, his digging speed on hard soil is \frac{5}{3} meters per day. On soft soil his speed would be \frac{5}{3}*\frac{6}{5}= \frac{6}{3} meters per day or 6 meters in 3 days. If one digger can dig 6 meters of a trench in 3 days then we need \frac{180}{3} = 30 diggers to dig the entire 180-meter long trench in 3 days.

Here how do we arrive at the fraction \frac{6}{5}?

_________________

Welcome to GMAT Club! :)
Facebook TwitterGoogle+LinkedIn
Want to solve GMAT questions on the go? GMAT Club iPhone app will help.
Please read this before posting in GMAT Club Tests forum
Result correlation between real GMAT and GMAT Club Tests
Are GMAT Club Test sets ordered in any way?

Take 15 free tests with questions from GMAT Club, Knewton, Manhattan GMAT, and Veritas.

Find out what's new at GMAT Club - latest features and updates

GMAT Club team member
User avatar
Joined: 02 Sep 2009
Posts: 11566
Followers: 1796

Kudos [?]: 9578 [0], given: 826

GMAT Tests User CAT Tests
Top Member of the Month
Re: M11 #19 [#permalink] New post 03 May 2012, 22:09
Working at their normal constant rates, 20 diggers can dig a 100-meter long trench in hard soil in 3 days. A construction company ordered the diggers to dig a 180-meter long trench in soft soil. If diggers can work 20% faster in soft soil than in hard soil, how many diggers are required to complete this task in 3 days?

A. 25
B. 28
C. 29
D. 30
E. 32

20 diggers can dig a 100-meter long trench in hard soil in 3 days;
1 digger can dig a 100/20=5-meter long trench in hard soil in 3 days;
1 digger can dig a 5*1.2=6-meter long trench in soft soil in 3 days;

Therefore, to dig 180-meter long trench in soft soil in 3 days 180/6=30 diggers are required.

Answer; D.
_________________

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

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. NEW!!!

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. NEW!!!


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

Find out what's new at GMAT Club - latest features and updates

Re: M11 #19   [#permalink] 03 May 2012, 22:09
    Similar topics Author Replies Last post
Similar
Topics:
 New posts 2 M11 #03 dczuchta 2 01 Oct 2008, 15:20
Popular new posts 15 EXPERTS_POSTS_IN_THIS_TOPIC m11#9 amitdgr 10 01 Nov 2008, 08:23
This topic is locked, you cannot edit posts or make further replies. New EXPERTS_POSTS_IN_THIS_TOPIC m11,#8 ritula 13 11 Nov 2008, 23:35
Popular new posts 11 EXPERTS_POSTS_IN_THIS_TOPIC m11#30 georgechanhc 19 31 Dec 2008, 22:20
Popular new posts 10 EXPERTS_POSTS_IN_THIS_TOPIC M11 #26 topmbaseeker 31 24 Jan 2009, 14:18
Display posts from previous: Sort by

M11 #19

  Question banks Downloads My Bookmarks Reviews  
Print view
First unread post

Moderator: Bunuel

Search for:


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®.

Main navigation

GMAT Resources

Partners

MBA Resources

www.gmac.com|www.mba.com