It is currently 24 Feb 2018, 10:04

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

M05-14

  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: 43896
M05-14 [#permalink]

Show Tags

New post 15 Sep 2014, 23:25
Expert's post
25
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  75% (hard)

Question Stats:

56% (01:15) correct 44% (02:15) wrong based on 139 sessions

HideShow timer Statistics

Two cities, Kensington, MD and Reston, VA are 30 km apart. From both of these cities, simultaneously, two hikers start their journeys towards each other. They are walking at a constant speed of 5 km/hour each. Simultaneously, a fly leaves the city of Kensington. It flies at the speed of 10 km/hour and passes the hiker from its city. When it reaches the Reston hiker, it turns around and flies back to the Kensington hiker. It keeps doing so until the hikers meet. If the fly lands on the shoulder of the Kensington hiker as he continues his journey to Reston at the moment the two hikers meet, how many kilometers has the fly flown?

A. 25
B. 30
C. 37.5
D. 45
E. 60
[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
5 KUDOS received
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 43896
Re M05-14 [#permalink]

Show Tags

New post 15 Sep 2014, 23:25
5
This post received
KUDOS
Expert's post
2
This post was
BOOKMARKED
Official Solution:

Two cities, Kensington, MD and Reston, VA are 30 km apart. From both of these cities, simultaneously, two hikers start their journeys towards each other. They are walking at a constant speed of 5 km/hour each. Simultaneously, a fly leaves the city of Kensington. It flies at the speed of 10 km/hour and passes the hiker from its city. When it reaches the Reston hiker, it turns around and flies back to the Kensington hiker. It keeps doing so until the hikers meet. If the fly lands on the shoulder of the Kensington hiker as he continues his journey to Reston at the moment the two hikers meet, how many kilometers has the fly flown?

A. 25
B. 30
C. 37.5
D. 45
E. 60


Calculate how long the fly was flying. We know that the fly flew until the two hikers met and they did so after \(\frac{30}{5+5} = 3\) hours. Thus it was flying for 3 hours at 10 km/h and covered a distance of 30 km.


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

1 KUDOS received
Intern
Intern
avatar
B
Joined: 31 Jul 2016
Posts: 19
Re: M05-14 [#permalink]

Show Tags

New post 25 Dec 2016, 13:44
1
This post received
KUDOS
Damn!!! I feel so stupid seeing this solution, (I literally was calculating to and fro distance covered by the fly) Sometimes it just doesn't strike you in the test environment.
Intern
Intern
avatar
B
Joined: 02 Sep 2016
Posts: 1
GMAT ToolKit User Premium Member Reviews Badge
Re: M05-14 [#permalink]

Show Tags

New post 26 Jan 2017, 05:58
The answer is 45. On the second half the fly travels with 5Km/h.
Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 43896
Re: M05-14 [#permalink]

Show Tags

New post 26 Jan 2017, 06:03
Manager
Manager
avatar
B
Joined: 23 Nov 2016
Posts: 76
Location: United States (MN)
GMAT 1: 760 Q50 V42
GPA: 3.51
Premium Member
Re: M05-14 [#permalink]

Show Tags

New post 06 Mar 2017, 09:21
1
This post was
BOOKMARKED
Bunuel, that is an amazing shortcut. For those who didn't see the shortcut (like me), this is also the sum of a geometric series, with the first term a = 20, and the common ratio r= 1/3. 20*(1/(1-1/3)) = 30.
Intern
Intern
avatar
Joined: 15 Mar 2017
Posts: 1
Re M05-14 [#permalink]

Show Tags

New post 05 Sep 2017, 16:45
I think this is a high-quality question and the explanation isn't clear enough, please elaborate. ...But the explanation is very poor. What is the most efficient way to calculate the answer within 2 minutes? I had to draw this out and took way longer.
Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 43896
Re: M05-14 [#permalink]

Show Tags

New post 05 Sep 2017, 19:38
nealpatel89 wrote:
I think this is a high-quality question and the explanation isn't clear enough, please elaborate. ...But the explanation is very poor. What is the most efficient way to calculate the answer within 2 minutes? I had to draw this out and took way longer.


The solution given IS in fact shortest and most efficient way to get the answer. It should take no more than 30 seconds. So, please re-read the solution and try to understand the logic behind it.
_________________

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: 11 Aug 2017
Posts: 3
CAT Tests
Re: M05-14 [#permalink]

Show Tags

New post 29 Oct 2017, 03:45
hi bunnel,

in the first 2 hrs the fly travels 20 kms and at this point it reaches the man from Reston who has travelled 10 kms in this time.After this when it travels back along with the man from Reston,both men meet at another 5 kms.
So the fly has travelled 25 kms when it lands on the shoulder of the man from Kensington.

Where am i going wrong?
Pls reply
Expert Post
1 KUDOS received
Math Expert
User avatar
D
Joined: 02 Aug 2009
Posts: 5662
Re: M05-14 [#permalink]

Show Tags

New post 29 Oct 2017, 05:50
1
This post received
KUDOS
Expert's post
yamini.mv wrote:
hi bunnel,

in the first 2 hrs the fly travels 20 kms and at this point it reaches the man from Reston who has travelled 10 kms in this time.After this when it travels back along with the man from Reston,both men meet at another 5 kms.
So the fly has travelled 25 kms when it lands on the shoulder of the man from Kensington.

Where am i going wrong?
Pls reply



Hi..
Where you are going wrong is Taking speed of fly also as 5km/h after it meets the other hiker

So the fly travels 20km and meets second hiker.
Then it turns back and moves with 10km/h to meet first hiker, and it will not meet him at 5km /h but they travel distance of 10km in combined speed of 10+5..... Time taken =10/15, so fly will travel 10*10/15 in this time..
And again turn back and move..

Best method is to find after how much time these hikers meet as nothing is hampering their move and then see how much that fly will travel in that time.
So distance 30 combined speed 5+5=10, so time taken =20/10=3h..
In 3h fly will travel 10*3=30
Ans
_________________

Absolute modulus :http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html


BANGALORE/-

Intern
Intern
avatar
B
Joined: 03 Oct 2016
Posts: 3
Location: India
Schools: ISB '19 (S)
GMAT 1: 680 Q47 V36
GPA: 2.67
Reviews Badge
Re: M05-14 [#permalink]

Show Tags

New post 20 Dec 2017, 22:11
This my first reply and let me tell the method given in the explanation is the best way to get the answer. I went into deep calculations and even though I got the answer I wouldn't have even gone down that road in the real test.
Re: M05-14   [#permalink] 20 Dec 2017, 22:11
Display posts from previous: Sort by

M05-14

  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®.