GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 13 Nov 2018, 14:30

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 in November
PrevNext
SuMoTuWeThFrSa
28293031123
45678910
11121314151617
18192021222324
2526272829301
Open Detailed Calendar
  • Essential GMAT Time-Management Hacks

     November 14, 2018

     November 14, 2018

     07:00 PM PST

     08:00 PM PST

    Join the webinar and learn time-management tactics that will guarantee you answer all questions, in all sections, on time. Save your spot today! Nov. 14th at 7 PM PST
  • $450 Tuition Credit & Official CAT Packs FREE

     November 15, 2018

     November 15, 2018

     10:00 PM MST

     11:00 PM MST

    EMPOWERgmat is giving away the complete Official GMAT Exam Pack collection worth $100 with the 3 Month Pack ($299)

M70-23

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

Hide Tags

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 50572
M70-23  [#permalink]

Show Tags

New post 03 Sep 2018, 04:46
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

80% (02:03) correct 20% (04:33) wrong based on 5 sessions

HideShow timer Statistics

A circular pond is drained through a tiny hole in its middle, such that its diameter becomes smaller at a constant rate of \(x\) meters per second. If it takes the pond \(y\) seconds to fully drain, what was its initial circumference?


A. \(\frac{2\pi y}{x}\)
B. \(\pi xy\)
C. \(\frac{\pi xy}{2}\)
D. \(2\pi xy\)
E. \(4\pi xy\)

_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

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?
Extra-hard Quant Tests with Brilliant Analytics

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 50572
Re M70-23  [#permalink]

Show Tags

New post 03 Sep 2018, 04:46
Official Solution:


A circular pond is drained through a tiny hole in its middle, such that its diameter becomes smaller at a constant rate of \(x\) meters per second. If it takes the pond \(y\) seconds to fully drain, what was its initial circumference?


A. \(\frac{2\pi y}{x}\)
B. \(\pi xy\)
C. \(\frac{\pi xy}{2}\)
D. \(2\pi xy\)
E. \(4\pi xy\)


We’ll go for ALTERNATIVE because there are variables in all the answers.

If we pick \(x = 1\) and \(y = 2\), it takes 2 seconds for the pool to drain, and each second represents 1 meter of the diameter, so the diameter is 2 × 1 = 2 meters long. Since the circumference is \(\pi × diameter\), the circle’s circumference is \(\pi × 2 = 2\pi\). Let’s check the answers: (A) \(\pi\) − No!; (B) \(2\pi\) − possible, but we must check the other answer choices; (C) \(\pi\) – Nope!; (D) \(4\pi\) – No!; (E) \(8\pi\) – Eliminated! We are left with answer choice (B).


Answer: B
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

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?
Extra-hard Quant Tests with Brilliant Analytics

Intern
Intern
avatar
B
Joined: 15 Aug 2012
Posts: 42
Schools: AGSM '19
GMAT ToolKit User CAT Tests
Re: M70-23  [#permalink]

Show Tags

New post 04 Sep 2018, 15:15
1
Bunuel wrote:
Official Solution:


A circular pond is drained through a tiny hole in its middle, such that its diameter becomes smaller at a constant rate of \(x\) meters per second. If it takes the pond \(y\) seconds to fully drain, what was its initial circumference?


A. \(\frac{2\pi y}{x}\)
B. \(xy\)
C. \(\frac{\pi xy}{2}\)
D. \(2\pi xy\)
E. \(4\pi xy\)


We’ll go for ALTERNATIVE because there are variables in all the answers.

If we pick \(x = 1\) and \(y = 2\), it takes 2 seconds for the pool to drain, and each second represents 1 meter of the diameter, so the diameter is 2 × 1 = 2 meters long. Since the circumference is \(\pi × diameter\), the circle’s circumference is \(\pi × 2 = 2\pi\). Let’s check the answers: (A) \(\pi\) − No!; (B) \(2\pi\) − possible, but we must check the other answer choices; (C) \(\pi\) – Nope!; (D) \(4\pi\) – No!; (E) \(8\pi\) – Eliminated! We are left with answer choice (B).


Answer: B


Hi Bunuel
If B is the right answer, shouldn't it be pi*x*y?
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 50572
Re: M70-23  [#permalink]

Show Tags

New post 04 Sep 2018, 20:02
rajudantuluri wrote:
Bunuel wrote:
Official Solution:


A circular pond is drained through a tiny hole in its middle, such that its diameter becomes smaller at a constant rate of \(x\) meters per second. If it takes the pond \(y\) seconds to fully drain, what was its initial circumference?


A. \(\frac{2\pi y}{x}\)
B. \(xy\)
C. \(\frac{\pi xy}{2}\)
D. \(2\pi xy\)
E. \(4\pi xy\)


We’ll go for ALTERNATIVE because there are variables in all the answers.

If we pick \(x = 1\) and \(y = 2\), it takes 2 seconds for the pool to drain, and each second represents 1 meter of the diameter, so the diameter is 2 × 1 = 2 meters long. Since the circumference is \(\pi × diameter\), the circle’s circumference is \(\pi × 2 = 2\pi\). Let’s check the answers: (A) \(\pi\) − No!; (B) \(2\pi\) − possible, but we must check the other answer choices; (C) \(\pi\) – Nope!; (D) \(4\pi\) – No!; (E) \(8\pi\) – Eliminated! We are left with answer choice (B).


Answer: B


Hi Bunuel
If B is the right answer, shouldn't it be pi*x*y?


Yes. \(\pi\) was missing. Edited. Thank you.
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

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?
Extra-hard Quant Tests with Brilliant Analytics

Intern
Intern
avatar
Joined: 04 Oct 2018
Posts: 1
Re: M70-23  [#permalink]

Show Tags

New post 31 Oct 2018, 16:47
In every second diameter reduces by X, hence radius reduces by X/2. So, in Y sec radius reduces by XY/2. This means the original radius was XY/2.
Hence circumference is 2pieXY/2 = XYpie.

Pl Comment
GMAT Club Bot
Re: M70-23 &nbs [#permalink] 31 Oct 2018, 16:47
Display posts from previous: Sort by

M70-23

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

Moderators: chetan2u, Bunuel



Copyright

GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| 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®.