Summer is Coming! Join the Game of Timers Competition to Win Epic Prizes. Registration is Open. Game starts Mon July 1st.
close

It is currently 18 Jul 2019, 06:22
Register
GMAT Club Tests
Decision Tracker
My Rewards
New comers' posts
New posts
Unanswered

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.

Go to My Error Log Learn more
Close

Request Expert Reply

Confirm Cancel
CLICK HERE TO HIDE/SHOW EVENTS

If 1/2 of the air in a tank is removed with each stroke of a

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
  Sort by Date Sort by Kudos  
Search for:
 
Print view
First unread post
Author Message
TAGS:

Hide Tags

Find Similar Topics 
Manager
Manager
avatar
Joined: 23 Mar 2008
Posts: 211
If 1/2 of the air in a tank is removed with each stroke of a  [#permalink]

Show Tags

New post Updated on: 13 May 2014, 06:32
3
14
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

64% (01:14) correct 36% (01:11) wrong based on 467 sessions

HideShow timer Statistics


If 1/2 of the air in a tank is removed with each stroke of a vacuum pump, what fraction of the original amount of air has been removed after 4 strokes ?

A. 15/16
B. 7/8
C. 1/4
D. 1/8
E. 1/16
Spoiler: OA

Originally posted by puma on 24 Jun 2008, 13:16.
Last edited by Bunuel on 13 May 2014, 06:32, edited 1 time in total.
Renamed the topic, edited the question, added the OA and moved to PS forum.
Most Helpful Community Reply
Current Student
avatar
Joined: 26 May 2005
Posts: 484
Re: Need Help - Fractions  [#permalink]

Show Tags

New post 09 Jun 2011, 11:49
4
2
srivats212 wrote:
Could someone please help me out with the below problem:

If 1/2 of the air in a tank is removed with each stroke of a vacuum pump, what fraction of the original amount of air has been removed after 4 strokes?

A. 15/16
B. 7/8
C. 1/4
D. 1/8
E. 1/16

This question is actually from the OG 12th edition. Am not able to understand the explanation given in OG for this problem. Could someone please explain in detail as to how to solve this


The best thing to do here is plug in
Assume that there is 16 units of air in the tank
first stroke = 1/2*16 = 8 ( we are left ith 8 now)
second stroke = 1/2*8 = 4( left ith 4 units now)
third stoke = 1/2*4 = 2( left with 2 units)
4th stroke = 1/2* 2 = 1 (left with 1 unit)

total units removed = 8+4+2+1 = 15
total unis in the tank at the begining = 16
thus its A . 15/16

Hope this helps
General Discussion
SVP
SVP
User avatar
B
Joined: 30 Apr 2008
Posts: 1782
Location: Oklahoma City
Schools: Hard Knocks
Re: tank  [#permalink]

Show Tags

New post 24 Jun 2008, 13:18
3
A

First you have 1

so
first stroke = 1/2
second stroke = 1/4
third stroke = 1/8
fourth stroke = 1/16

8/16 + 4/16 + 2/16 + 1/16 = 15/16

puma wrote:
if 1/2 of the air in a tank is removed with each stroke of a vacuum pump, what fraction of the original amount of the air has been removed after 4 strokes?

A) 15/16
B) 7/8
C) 1/4
D) 1/8
E) 1/16

_________________
------------------------------------
J Allen Morris
**I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a$$.

GMAT Club Premium Membership - big benefits and savings
Signature Read More
Intern
Intern
avatar
Joined: 30 Jul 2007
Posts: 31
Re: tank  [#permalink]

Show Tags

New post 24 Jun 2008, 13:58
1
puma wrote:
if 1/2 of the air in a tank is removed with each stroke of a vacuum pump, what fraction of the original amount of the air has been removed after 4 strokes?

A) 15/16
B) 7/8
C) 1/4
D) 1/8
E) 1/16


I get A, too.

Let X = air in the tank.

Plug in 240 = X.

First stroke = 1/2 * 240 = 120
Second stroke = 1/2 * 120 = 60
Third stroke = 1/2 * 60 = 30
Fourth stroke = 1/2 * 30 = 15

So 15 remains, which is the amount of air left.

240 - 15 = 225 (amount of air removed). 225/240 = 15/16
Manager
Manager
avatar
Joined: 27 Apr 2008
Posts: 170
Re: Need Help - Fractions  [#permalink]

Show Tags

New post 09 Jun 2011, 11:52
1
1
This is a decay-type problem...the tank is halved after each stroke. Therefore:

(0.5)^4 = 1/16 --> 0.5 for halving, 4 for strokes

so 1/16 of air is left in the tank => 15/16 of the air was removed
Intern
Intern
avatar
Joined: 04 May 2011
Posts: 9
GMAT ToolKit User
Re: Need Help - Fractions  [#permalink]

Show Tags

New post 09 Jun 2011, 12:10
1
Oh, I get it..! Thanks..!!!
I think the catch over here is.."the tank is halved after each stroke"....failed to understand the question properly.
Thought that a single stoke halves the air in it...so after 2 strokes guessed there wont be any air in it :x
Manager
Manager
avatar
Joined: 08 Sep 2010
Posts: 111
Re: Need Help - Fractions  [#permalink]

Show Tags

New post 09 Jun 2011, 21:30
3
1
A - 15/16..

Left After 1st stroke = 1/2
Left After 2nd stroke = 1/2 * 1/2 = 1/4
Left After 3rd stroke = 1/2 * 1/4 = 1/8
Left After 4th stroke = 1/2 * 1/8 = 1/16

So removed = 1- 1/16 = 15/16
_________________
My will shall shape the future. Whether I fail or succeed shall be no man's doing but my own.

If you like my explanations award kudos.
Signature Read More
Manager
Manager
avatar
Joined: 27 Apr 2008
Posts: 170
Re: Need Help - Fractions  [#permalink]

Show Tags

New post 10 Jun 2011, 09:40
As they say, the devil is in the details!
Manager
Manager
avatar
Joined: 12 Oct 2009
Posts: 139
Schools: Columbia, INSEAD, RSM, LBS
Re: Need Help - Fractions  [#permalink]

Show Tags

New post 10 Jun 2011, 11:42
By the 4th stroke the the air remaining is 1/16 , so what has been removed is 15/16
Manager
Manager
avatar
Joined: 05 Oct 2011
Posts: 157
GMAT ToolKit User Reviews Badge
Re: Need Help - Fractions  [#permalink]

Show Tags

New post 02 Nov 2011, 10:46
1st stroke 1/2
2nd stroke 1/4
3rd stroke 1/8
4th stroke 1/16
total: (8+4+2+1)/16=15/16
Director
Director
User avatar
Status: Everyone is a leader. Just stop listening to others.
Joined: 22 Mar 2013
Posts: 744
Location: India
GPA: 3.51
WE: Information Technology (Computer Software)
Reviews Badge
Re: Need Help - Fractions  [#permalink]

Show Tags

New post 24 Sep 2013, 02:31
Better use compound interest formula.

Remaing amount = P ( 1 - R/100)^n

Let P is 100 ( 1 - 50/100)^4
Remaining amount = 100(1/16)

if 1/16 of 100 is remaining means 1-1/16 = 15/16 is lost.
_________________
Piyush K
-----------------------
Our greatest weakness lies in giving up. The most certain way to succeed is to try just one more time. ― Thomas A. Edison
Don't forget to press--> Kudos :)
My Articles: 1. WOULD: when to use? | 2. All GMATPrep RCs (New)
Tip: Before exam a week earlier don't forget to exhaust all gmatprep problems specially for "sentence correction".
Signature Read More
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 56251
CAT Tests
Top Member of the Month
Re: If 1/2 of the air in a tank is removed with each stroke of a  [#permalink]

Show Tags

New post 13 May 2014, 06:32
1
puma wrote:
If 1/2 of the air in a tank is removed with each stroke of a vacuum pump, what fraction of the original amount of air has been removed after 4 strokes ?

A. 15/16
B. 7/8
C. 1/4
D. 1/8
E. 1/16


Similar questions to practice:
if-2-3-of-the-air-in-a-tank-is-removed-with-each-stroke-of-a-128432.html
if-3-4-of-the-mineral-deposits-in-a-reservoir-of-water-are-97300.html
on-january-1-2076-lake-loser-contains-x-liters-of-water-b-82667.html

Hope it helps.
_________________
New to the GMAT CLUB Forum?
Posting Rules: QUANTITATIVE | VERBAL. Guides and Resources: QUANTITATIVE | VERBAL | Ultimate GMAT Quantitative Megathread | All You Need for Quant

Questions' Banks and Collection:
PS: Standard deviation | Tough Problem Solving Questions With Solutions | Probability and Combinations Questions With Solutions | Tough and tricky exponents and roots questions | 12 Easy Pieces (or not?) | Bakers' Dozen | Algebra set | Mixed Questions | Fresh Meat
DS: DS Standard deviation | Inequalities | 700+ GMAT Data Sufficiency Questions With Explanations | Tough and tricky exponents and roots questions | The Discreet Charm of the DS | Devil's Dozen!!! | Number Properties set | New DS set
MIXED: GMAT Club's Complete Questions' Bank | SEVEN SAMURAI OF 2012 | Tricky questions from previous years. | Special Questions' Directory | Best Of The Best Of 2017 | The Best Of Quant of 2016 | 20 hardest and 20 best questions of 2015 | 15 best topics of 2015 | Seven Samurai of 2012 | GMAT Probability Questions

What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics
Signature Read More
SVP
SVP
User avatar
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1787
Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Re: If 1/2 of the air in a tank is removed with each stroke of a  [#permalink]

Show Tags

New post 01 Aug 2014, 00:57
Let say total air = 1

Total air removed

\(= \frac{1}{2} + \frac{1}{2^2} + \frac{1}{2^3} + \frac{1}{2^4}\)

\(= \frac{15}{16}\)

Answer = A
_________________
Kindly press "+1 Kudos" to appreciate :)
Signature Read More
Board of Directors
User avatar
P
Joined: 17 Jul 2014
Posts: 2539
Location: United States (IL)
Concentration: Finance, Economics
Schools: Stanford '20 (WD)
GMAT 1: 650 Q49 V30
GPA: 3.92
WE: General Management (Transportation)
GMAT ToolKit User Reviews Badge
If 1/2 of the air in a tank is removed with each stroke of a  [#permalink]

Show Tags

New post 23 Jan 2017, 16:50
puma wrote:
If 1/2 of the air in a tank is removed with each stroke of a vacuum pump, what fraction of the original amount of air has been removed after 4 strokes ?

A. 15/16
B. 7/8
C. 1/4
D. 1/8
E. 1/16


let's assign a nice number..16 (divisible by 2 and 4), for total Air..
after 1st stroke, we are left with 8
after 2nd stroke, we are left with 4
after 3rd stroke, we are left with 2
after 4th stroke, we are left with 1

we removed 15 parts out of 16.
A: 15/16
_________________
Image
Signature Read More
Manager
Manager
avatar
S
Joined: 17 Aug 2012
Posts: 123
Location: India
Concentration: General Management, Strategy
Schools: Copenhagen, ESMT"19
GPA: 3.75
WE: Consulting (Energy and Utilities)
GMAT ToolKit User
Re: If 1/2 of the air in a tank is removed with each stroke of a  [#permalink]

Show Tags

New post 25 Feb 2017, 10:40
Let initial air be X

after 1st stroke air left x/2
after 2nd stroke air left x/4
after 3rd stroke air left x/8
after 4th stroke air left x/16

air removed = original - air left
=x - x/16 = 15x/16
EMPOWERgmat Instructor
User avatar
V
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 14567
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Re: If 1/2 of the air in a tank is removed with each stroke of a  [#permalink]

Show Tags

New post 19 Mar 2018, 11:11
Hi All,

TESTing Values will work well on this question. A quick look at the answers tells us that the common denominator for all 5 options is 16; THAT is a huge clue that 16 would be a great number to TEST.

We're told that 1/2 of the air in a tank is removed with each stroke. We're asked what fraction has been removed after 4 strokes….

Full = 16
1st = 16-8 = 8 left
2nd = 8-4 = 4 left
3rd = 4-2 = 2 left
4th = 2-1 = 1 left

So 1/16 is LEFT; thus, 15/16 was REMOVED

Final Answer:
Spoiler: ::
A


GMAT assassins aren't born, they're made,
Rich
_________________
760+: Learn What GMAT Assassins Do to Score at the Highest Levels
Contact Rich at: Rich.C@empowergmat.com
*****Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!*****

Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save $75 + GMAT Club Tests Free
  Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/
Signature Read More
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 11693
Re: If 1/2 of the air in a tank is removed with each stroke of a  [#permalink]

Show Tags

New post 04 Jul 2019, 03:46
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.
_________________
GMAT Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources
Signature Read More
GMAT Club Bot
Re: If 1/2 of the air in a tank is removed with each stroke of a   [#permalink] 04 Jul 2019, 03:46
Print view
First unread post
Display posts from previous: Sort by

If 1/2 of the air in a tank is removed with each stroke of a

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

Moderators: chetan2u, Gladiator59, VeritasKarishma, Bunuel, generis

Search for:





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

Main navigation

GMAT Resources

Partners

MBA Resources

www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions