It is currently 22 Feb 2018, 09:02

TODAY:

MIT Sloan Releasing 1st Wave of Interview Invites - Join GMATClub CHAT for Live Updates


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

M08-25

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

Hide Tags

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 43866
M08-25 [#permalink]

Show Tags

New post 15 Sep 2014, 23:38
Expert's post
12
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  65% (hard)

Question Stats:

70% (01:36) correct 30% (02:08) wrong based on 128 sessions

HideShow timer Statistics

If the diameter of each of the car's wheels is 20 inches, what was the approximate average speed of the car in km/h if after the two-hour journey each wheel made 75,000 revolutions? (1 inch = 0.0254 meter)

A. 32
B. 41
C. 59
D. 74
E. 88
[Reveal] Spoiler: OA

_________________

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

Expert Post
1 KUDOS received
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 43866
Re M08-25 [#permalink]

Show Tags

New post 15 Sep 2014, 23:38
1
This post received
KUDOS
Expert's post
Official Solution:

If the diameter of each of the car's wheels is 20 inches, what was the approximate average speed of the car in km/h if after the two-hour journey each wheel made 75,000 revolutions? (1 inch = 0.0254 meter)

A. 32
B. 41
C. 59
D. 74
E. 88


The wheel's radius in meters = \(\frac{20 \text{ inches } * 0.0254}{2} = 0.254 \approx 0.25\) meters.

The wheel's circumference = \(2\pi(0.25) = 0.5\pi \approx \frac{3}{2} = 1.5\) meters.

The distance in kilometers = \(75000*\frac{1.5}{1000} = 75*1.5 = 112.5 \approx 113\) km.

The average speed in km/h = \(\frac{113}{2} = 56.5\) km/h which is closest to choice C.


Answer: C
_________________

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: 11 Feb 2015
Posts: 5
Re: M08-25 [#permalink]

Show Tags

New post 16 Jun 2015, 07:42
Hi Bunuel,

I am having trouble understanding this problem visually. Based on the solution, I can see we calculated the distance that the "wheel" travel. However, we want to calculate the distance that the car travel. Are they the same? I draw out how the wheel rotate on paper and having trouble to think of these two distances are the same. Could you help me clear this out?
Expert Post
1 KUDOS received
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 43866
Re: M08-25 [#permalink]

Show Tags

New post 16 Jun 2015, 09:44
1
This post received
KUDOS
Expert's post
1
This post was
BOOKMARKED
Tsuruga wrote:
Hi Bunuel,

I am having trouble understanding this problem visually. Based on the solution, I can see we calculated the distance that the "wheel" travel. However, we want to calculate the distance that the car travel. Are they the same? I draw out how the wheel rotate on paper and having trouble to think of these two distances are the same. Could you help me clear this out?


I thinks similar problems might help:
a-circular-rim-28-inches-in-diameter-rotates-the-same-number-65106.html
two-wheels-are-connected-via-a-conveyor-belt-the-larger-133697.html
how-long-in-minutes-did-it-take-a-bicycle-wheel-to-roll-130026.html
what-is-the-number-of-360-degree-rotations-that-a-bicycle-wh-166668.html
the-circumference-of-the-front-wheel-of-a-cart-is-30-ft-long-90588.html
a-point-on-the-edge-of-a-fan-blade-that-is-rotating-in-a-plane-is-65505.html
m10-183873.html
at-the-same-time-sue-began-rolling-a-wheelbarrow-from-x-to-y-nancy-199350.html
_________________

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

Manager
Manager
User avatar
Joined: 05 Jul 2015
Posts: 107
Concentration: Real Estate, International Business
GMAT 1: 600 Q33 V40
GPA: 3.3
Re: M08-25 [#permalink]

Show Tags

New post 21 Feb 2016, 17:13
The way I skipped some of the math:

piD = Circumference = 20pi

20 * 75,000 *pi = 150(plus a lot of zeroes) *pi

.025 = (1/4) minus a couple of zeroes. So take away a couple of zeroes from the big number and divide by four and you get close to 20. 20*pi = close to 60

Answer C
Intern
Intern
avatar
Joined: 06 Sep 2016
Posts: 3
Re: M08-25 [#permalink]

Show Tags

New post 21 Nov 2016, 20:58
poor quality question
Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 43866
Re: M08-25 [#permalink]

Show Tags

New post 21 Nov 2016, 21:29
Intern
Intern
avatar
B
Joined: 28 Jan 2017
Posts: 6
Re: M08-25 [#permalink]

Show Tags

New post 05 Mar 2017, 12:38
hie
Re: M08-25   [#permalink] 05 Mar 2017, 12:38
Display posts from previous: Sort by

M08-25

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

Moderators: chetan2u, Bunuel



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®.