It is currently 20 Oct 2017, 13:10

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.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

In a stack of boards at a lumber yard, the 20th board counting from th

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Director
Director
User avatar
Status: No dream is too large, no dreamer is too small
Joined: 14 Jul 2010
Posts: 615

Kudos [?]: 1134 [0], given: 39

In a stack of boards at a lumber yard, the 20th board counting from th [#permalink]

Show Tags

New post 17 Jun 2011, 05:09
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

53% (00:38) correct 47% (00:44) wrong based on 95 sessions

HideShow timer Statistics

In a stack of boards at a lumber yard, the 20th board counting from the top of the stack is immediately below the 16th board counting from the bottom of the stack. how many boards are in the stack?

A) 38

B) 36

C) 35

D) 34

E) 32
[Reveal] Spoiler: OA

_________________

Collections:-
PSof OG solved by GC members: http://gmatclub.com/forum/collection-ps-with-solution-from-gmatclub-110005.html
DS of OG solved by GC members: http://gmatclub.com/forum/collection-ds-with-solution-from-gmatclub-110004.html
100 GMAT PREP Quantitative collection http://gmatclub.com/forum/gmat-prep-problem-collections-114358.html
Collections of work/rate problems with solutions http://gmatclub.com/forum/collections-of-work-rate-problem-with-solutions-118919.html
Mixture problems in a file with best solutions: http://gmatclub.com/forum/mixture-problems-with-best-and-easy-solutions-all-together-124644.html

Kudos [?]: 1134 [0], given: 39

1 KUDOS received
Manager
Manager
User avatar
Joined: 19 Nov 2010
Posts: 88

Kudos [?]: 174 [1], given: 9

Re: In a stack of boards at a lumber yard, the 20th board counting from th [#permalink]

Show Tags

New post 17 Jun 2011, 13:08
1
This post received
KUDOS
1 2 3 ... 14 15 16 ...................
..............20 19 ................. 1

So the number of boards = 20+14 =34

Kudos [?]: 174 [1], given: 9

Director
Director
User avatar
P
Joined: 04 Dec 2015
Posts: 696

Kudos [?]: 303 [0], given: 261

Location: India
Concentration: Technology, Strategy
Schools: ISB '19, IIMA , IIMB, XLRI
WE: Information Technology (Consulting)
GMAT ToolKit User
Re: In a stack of boards at a lumber yard, the 20th board counting from th [#permalink]

Show Tags

New post 04 Jul 2017, 15:44
Baten80 wrote:
In a stack of boards at a lumber yard, the 20th board counting from the top of the stack is immediately below the 16th board counting from the bottom of the stack. how many boards are in the stack?

A) 38

B) 36

C) 35

D) 34

E) 32


A board is 20th board counting from the top of the stack . Therefore it will have \(19\) boards above it.

Same board is immediately below the \(16th\) board counting from the bottom of the stack.

Therefore it is on \(15th\) number from bottom of the stack and it will have \(14\) boards below it.

Total number of boards in stack \(= 19 + 14 + 1 = 34\)

Answer (D)...

_________________
Please Press "+1 Kudos" to appreciate. :)

Kudos [?]: 303 [0], given: 261

Director
Director
avatar
P
Joined: 22 May 2016
Posts: 819

Kudos [?]: 266 [0], given: 552

In a stack of boards at a lumber yard, the 20th board counting from th [#permalink]

Show Tags

New post 05 Jul 2017, 15:42
Baten80 wrote:
In a stack of boards at a lumber yard, the 20th board counting from the top of the stack is immediately below the 16th board counting from the bottom of the stack. how many boards are in the stack?

A) 38

B) 36

C) 35

D) 34

E) 32
Attachment:
stack of boards.jpg
stack of boards.jpg [ 797.06 KiB | Viewed 409 times ]


After 20 seconds of trying to do the math in my head, I sketched quickly and it got a lot easier.

I've attached a diagram.

Though there are two columns, they represent one stack.

If you were standing in front of this one stack to count boards, for the left column, you would put your finger on the top board and count downward. The right column is the same stack, only this time you have reached down and started counting from the bottom upwards. I slid the two apart to figure out where GREEN and YELLOW fell in relation to boards above and below, and to get arithmetic correct.


Call the board that is 20th counting down from the top GREEN.

That GREEN board sits one below the board that is 16th counting up from the bottom. Call that 16th-from-bottom YELLOW.

GREEN has 19 boards above it. YELLOW has 15 boards below it.

But there is overlap: GREEN takes the ordinal "counting place" of 15th board from bottom (crossed out in diagram to indicate it shouldn't be counted), and

YELLOW takes the ordinal counting place of 19th board from top counting down (also crossed out).

Don't think about the blacked out parts. In ordinal (nth) terms, they don't match, and they'll confuse, which is precisely the point of this question.

So we have 18 + 1 + 1 + 14 = 34.

Answer D

Hope it helps.

Edited to add italicized text.

Kudos [?]: 266 [0], given: 552

Expert Post
Target Test Prep Representative
User avatar
S
Status: Head GMAT Instructor
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 1545

Kudos [?]: 837 [0], given: 5

Re: In a stack of boards at a lumber yard, the 20th board counting from th [#permalink]

Show Tags

New post 14 Jul 2017, 10:42
Baten80 wrote:
In a stack of boards at a lumber yard, the 20th board counting from the top of the stack is immediately below the 16th board counting from the bottom of the stack. how many boards are in the stack?

A) 38

B) 36

C) 35

D) 34

E) 32


If the 20th board counting from the top of the stack is immediately below the 16th board counting from the bottom of the stack, then the 19th board counting from the top of the stack is exactly the 16th board counting from the bottom of the stack. In other words, there are 18 boards above the 16th board counting from the bottom of the stack. Thus, there are 18 + 16 = 34 boards in the stack.

Answer: D
_________________

Jeffery Miller
Head of GMAT Instruction

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Kudos [?]: 837 [0], given: 5

Re: In a stack of boards at a lumber yard, the 20th board counting from th   [#permalink] 14 Jul 2017, 10:42
Display posts from previous: Sort by

In a stack of boards at a lumber yard, the 20th board counting from th

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


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

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

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®.