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

It is currently 20 Jun 2013, 04:20
Customize  |  Hide

Search
Register
New posts
Unanswered

M23-29

  Question banks Downloads My Bookmarks Reviews  
  Oldest Best Reply
Search for:
 
Print view
First unread post
Author Message
Manager
Manager
Joined: 06 Jun 2010
Posts: 162
Followers: 2

Kudos [?]: 14 [0], given: 151

M23-29 [#permalink] New post 01 Mar 2013, 06:55
00:00

Question Stats:

0% (00:00) correct 100% (00:00) wrong based on 2 sessions
If 1 book was left when a pile of books was stacked in rows of 5, how many books are there in all?
(1) When the books were stacked in rows of 7, 1 book was left

(2) When the books were stacked in rows of 8, 4 books were left

I solved this using Remainder approach.
From question stmt: N/5

1.N/7 Remainder is 1
so find a number such that when N/5 and N/7 gives remainder of 1. Found N=36.Sufficient

2.N/8 Remainder is 4
so N/5 gives remainder 1 and N/8 gives remainder 4.Found N =36.Sufficient.

Can someone xplain whats wrong with my approach?
[Reveal] Spoiler: OA
1 KUDOS received
BSchool Thread Master
User avatar
Status: If you think you can, then eventually you WILL!
Joined: 05 Apr 2011
Posts: 399
Location: India
Concentration: Finance, Marketing
Schools: ISB '14 (D)
GMAT 1: 570 Q49 V19
GMAT 2: 700 Q51 V31
GPA: 3
WE: Information Technology (Computer Software)
Followers: 33

Kudos [?]: 139 [1] , given: 39

GMAT Tests User
Re: M23-29 [#permalink] New post 01 Mar 2013, 09:28
1
This post received
KUDOS
shreerajp99 wrote:
If 1 book was left when a pile of books was stacked in rows of 5, how many books are there in all?
(1) When the books were stacked in rows of 7, 1 book was left

(2) When the books were stacked in rows of 8, 4 books were left

I solved this using Remainder approach.
From question stmt: N/5

1.N/7 Remainder is 1
so find a number such that when N/5 and N/7 gives remainder of 1. Found N=36.Sufficient

2.N/8 Remainder is 4
so N/5 gives remainder 1 and N/8 gives remainder 4.Found N =36.Sufficient.

Can someone xplain whats wrong with my approach?


B = 5k + 1

STAT1
B = 7t + 1
5k + 1 =7t + 1
k = 7t/5
So, Those values of t which will give you integer value are the common solution.
So, t=5,10,15,20
k = 7,14,21,28,35,42,49,56,63,...
So, B = 36, 71,...

So, Not Sufficient as there are many possible values!

STAT2
B = 8s + 4
5k + 1 = 8s + 4
k = (8s + 3)/5
Those values of s which will give you integer value of k are solution.
s = 4, 9,14,19,24,...
k = 7, 15, 23,31,39, 47, 55, 63
So, B = 36, 76,...

So, Not Sufficient as there are many possible values!

Trying for C
k = 7 and 63 are the two solutions which are possible (actually there are more...)
B = 36, 316

So, Answer is E
Hope it helps!
_________________

ankit
you must believe

How to start GMAT preparations?
How to Improve Quant Score?
gmatclub topic tags
Check out my GMAT debrief
Thursdays with Ron link
Looking for a Quant tutor? Check out my post for the same!

Combined Formula Sheet :
Number Properties || Word Problems and PnC || Equations, Inequalities || Geometry

How to Solve :
Statistics || Reflection of a line || Remainder Problems

Re: M23-29   [#permalink] 01 Mar 2013, 09:28
Display posts from previous: Sort by

M23-29

  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