It is currently 19 Feb 2018, 23:55

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

At what speed was Erik running when he was at the halfway point of his

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

Hide Tags

2 KUDOS received
Senior Manager
Senior Manager
User avatar
Status: Math is psycho-logical
Joined: 07 Apr 2014
Posts: 432
Location: Netherlands
GMAT Date: 02-11-2015
WE: Psychology and Counseling (Other)
At what speed was Erik running when he was at the halfway point of his [#permalink]

Show Tags

New post 06 Feb 2015, 08:52
2
This post received
KUDOS
1
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

67% (00:34) correct 33% (00:45) wrong based on 196 sessions

HideShow timer Statistics

At what speed was Erik running when he was at the halfway point of his route?

1. Erik's route was 10 miles long and took him 2 hours to complete.
2. Erik ran at an average speed of 5 miles per hour on the route
[Reveal] Spoiler: OA
Senior Manager
Senior Manager
User avatar
Status: Math is psycho-logical
Joined: 07 Apr 2014
Posts: 432
Location: Netherlands
GMAT Date: 02-11-2015
WE: Psychology and Counseling (Other)
Re: At what speed was Erik running when he was at the halfway point of his [#permalink]

Show Tags

New post 06 Feb 2015, 08:54
1
This post was
BOOKMARKED
I found this one tricky... I chose the wrong answer, so I thought that others could make a similar mistake.
Sometimes, we have been doing sth again and again and we don't really notice what it means.

I think that this is a good question, because above all it tests our rational thinking and observation skills; and this is what the GMAT should mostly deal with.
VP
VP
avatar
P
Joined: 26 Mar 2013
Posts: 1428
Reviews Badge CAT Tests
Re: At what speed was Erik running when he was at the halfway point of his [#permalink]

Show Tags

New post 12 Feb 2015, 14:18
pacifist85 wrote:
At what speed was Erik running when he was at the halfway point of his route?

1. Erik's route was 10 miles long and took him 2 hours to complete.
2. Erik ran at an average speed of 5 miles per hour on the route



I could not understand why it is choice E. I think at any point it is the same speed 5 mph. So I think it is choice D
Expert Post
1 KUDOS received
EMPOWERgmat Instructor
User avatar
D
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 11036
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: 340 Q170 V170
Re: At what speed was Erik running when he was at the halfway point of his [#permalink]

Show Tags

New post 12 Feb 2015, 21:17
1
This post received
KUDOS
Expert's post
2
This post was
BOOKMARKED
Hi All,

On Test Day, it's extremely important to be clear on what the question actually asks you for. In most prompts in the Quant and Verbal sections, the question is straight-forward. In certain DS questions though, you have to think a bit more than normal about what you're asked for (and how it relates to what you're told).

Here, we're asked for Erik's speed at the halfway-point of his run. So we're asked for Erik's speed at that EXACT moment. We're NOT asked for his average speed.

Both Fact 1 and Fact 2 give us information about his AVERAGE speed, but that's not enough to figure out how fast Erik was running at the EXACT moment that he hit the halfway-point. Even combined, the information is redundant - and we still can't answer the question. Thus, the final answer is
[Reveal] Spoiler:
E


When dealing with DS questions, it helps to be a little cynical (or even suspicious). Think about what you KNOW and what you're ASKED FOR. Those details can be the difference between the right answer and the four wrong answers.

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

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/

***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************

Expert Post
1 KUDOS received
Veritas Prep GMAT Instructor
User avatar
G
Joined: 16 Oct 2010
Posts: 7941
Location: Pune, India
Re: At what speed was Erik running when he was at the halfway point of his [#permalink]

Show Tags

New post 12 Feb 2015, 21:25
1
This post received
KUDOS
Expert's post
pacifist85 wrote:
At what speed was Erik running when he was at the halfway point of his route?

1. Erik's route was 10 miles long and took him 2 hours to complete.
2. Erik ran at an average speed of 5 miles per hour on the route


Note that average speed does not tell you anything about the speed at any given time. Erik may have been running at a speed of 10 mph or at 2 mph at halfway point. Average speed only tells you the average over the entire time period.

Hence, the statements give us no useful information about speed at a particular instant.

Answer (E)
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for $199

Veritas Prep Reviews

1 KUDOS received
Intern
Intern
avatar
Joined: 22 Aug 2014
Posts: 42
GMAT ToolKit User
Re: At what speed was Erik running when he was at the halfway point of his [#permalink]

Show Tags

New post 12 Feb 2015, 22:13
1
This post received
KUDOS
pacifist85 wrote:
At what speed was Erik running when he was at the halfway point of his route?

1. Erik's route was 10 miles long and took him 2 hours to complete.
2. Erik ran at an average speed of 5 miles per hour on the route


Option E.

By looking at the qn, it seems easy and we tend to reply fast. There is a trick which is not mentioned.

1. It says Erik's route is 10 miles and time taken is 2 hours.

So d = 10 miles and t = 2 hours

2. Average speed = 5m/hr

No where it is mentioned that he is running at a constant speed and this where most of us would go wrong. So, let me assume S1 and S2 as the speeds during the course of 2 hours.

When S1 = S2 = 5 m/hr

When S1 <> S2, we get many scenarios

S1= 1m/hr & S2= 9m/hr
S1 = 2 & S2 = 8
S1 = 3 & S2 = 7
S1 = 4 & S2 = 6

and vice versa

Now all these speeds satisfy both conditions of covering 10m in 2 hours time. So coming back to the qn of speed at mid point, there are many possibilities being (1,2,3,4,5,6,7,8,9) and thus we come to a conclusion of data insufficiency. i.e Option E
VP
VP
avatar
P
Joined: 26 Mar 2013
Posts: 1428
Reviews Badge CAT Tests
Re: At what speed was Erik running when he was at the halfway point of his [#permalink]

Show Tags

New post 13 Feb 2015, 03:21
VeritasPrepKarishma wrote:
pacifist85 wrote:
At what speed was Erik running when he was at the halfway point of his route?

1. Erik's route was 10 miles long and took him 2 hours to complete.
2. Erik ran at an average speed of 5 miles per hour on the route


Note that average speed does not tell you anything about the speed at any given time. Erik may have been running at a speed of 10 mph or at 2 mph at halfway point. Average speed only tells you the average over the entire time period.

Hence, the statements give us no useful information about speed at a particular instant.

Answer (E)


Hi Karishma,

Thanks for sharing your thoughts but the question stimulated my mind to ask a question about calculating average speed.

Suppose the from the question above Erik run 4 miles in 1/2 hr then 6 miles in 1.5 hr So Which from the following is the right way to calculate the average speed

1- average Speed= (4+6)/(.5+1.5)= 5 mph

or

2- average speed = Speed in first leg + sped in second leg= 4/0.5 + 6/1.5 = 8+4= 12 mph

I'm confused.

Thanks in advance for your support
Expert Post
1 KUDOS received
Veritas Prep GMAT Instructor
User avatar
G
Joined: 16 Oct 2010
Posts: 7941
Location: Pune, India
Re: At what speed was Erik running when he was at the halfway point of his [#permalink]

Show Tags

New post 15 Feb 2015, 20:20
1
This post received
KUDOS
Expert's post
Mo2men wrote:
Hi Karishma,

Thanks for sharing your thoughts but the question stimulated my mind to ask a question about calculating average speed.

Suppose the from the question above Erik run 4 miles in 1/2 hr then 6 miles in 1.5 hr So Which from the following is the right way to calculate the average speed

1- average Speed= (4+6)/(.5+1.5)= 5 mph

or

2- average speed = Speed in first leg + sped in second leg= 4/0.5 + 6/1.5 = 8+4= 12 mph

I'm confused.

Thanks in advance for your support


Suppose in a race, you run slow for first part and fast for the second part, your average speed for the race will be medium, right? It cannot be super fast, right? So to get average speed, you can never add the two speeds.

Remember, Average Speed in every case = Total Distance/Total Time

If there is ever any confusion on which formula to use etc, always go back to this basic formula.

We have many other formulas such as weighted average of speed using time as weight, (a+b)/2, 2ab/(a+b) which are applicable in different scenarios but one thing that will ALWAYS work is Total Distance/Total Time.
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for $199

Veritas Prep Reviews

Intern
Intern
avatar
B
Joined: 26 Dec 2016
Posts: 27
Re: At what speed was Erik running when he was at the halfway point of his [#permalink]

Show Tags

New post 22 Jan 2018, 11:20
VeritasPrepKarishma wrote:
Mo2men wrote:
Hi Karishma,

Thanks for sharing your thoughts but the question stimulated my mind to ask a question about calculating average speed.

Suppose the from the question above Erik run 4 miles in 1/2 hr then 6 miles in 1.5 hr So Which from the following is the right way to calculate the average speed

1- average Speed= (4+6)/(.5+1.5)= 5 mph

or

2- average speed = Speed in first leg + sped in second leg= 4/0.5 + 6/1.5 = 8+4= 12 mph

I'm confused.

Thanks in advance for your support


Suppose in a race, you run slow for first part and fast for the second part, your average speed for the race will be medium, right? It cannot be super fast, right? So to get average speed, you can never add the two speeds.

Remember, Average Speed in every case = Total Distance/Total Time

If there is ever any confusion on which formula to use etc, always go back to this basic formula.

We have many other formulas such as weighted average of speed using time as weight, (a+b)/2, 2ab/(a+b) which are applicable in different scenarios but one thing that will ALWAYS work is Total Distance/Total Time.


Hi Karishma,

Do you mind giving examples of how and when those two formulas would be appropriately used?
Intern
Intern
avatar
B
Joined: 26 Dec 2016
Posts: 27
Re: At what speed was Erik running when he was at the halfway point of his [#permalink]

Show Tags

New post 22 Jan 2018, 11:29
Veritas Prep Problem as well:

Train A and Train B began traveling towards each other from opposite ends of a 500-mile long track at 1:00 PM. If Train A traveled at 35 miles per hour and Train B traveled at 25 miles per hour, at what time did the trains meet?

Official Solution

To solve this problem, try combining the rates of the two trains. The combined rate of Train A and Train B is 35 + 25 = 60 miles per hour. Now, use the formula: Distance = Rate x Time to find how many hours until the trains will meet. 500 miles / 60 miles per hour = 8 1/3
hours. If the trains started at 1:00 pm, they will meet at 9:20 pm, which is 8 1/3
hours later.

How come here we are combining speeds?
Expert Post
Veritas Prep GMAT Instructor
User avatar
G
Joined: 16 Oct 2010
Posts: 7941
Location: Pune, India
Re: At what speed was Erik running when he was at the halfway point of his [#permalink]

Show Tags

New post 22 Jan 2018, 22:23
Check this post for explanation of 4 average speed formulae:
https://www.veritasprep.com/blog/2015/0 ... -the-gmat/
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for $199

Veritas Prep Reviews

Expert Post
Veritas Prep GMAT Instructor
User avatar
G
Joined: 16 Oct 2010
Posts: 7941
Location: Pune, India
Re: At what speed was Erik running when he was at the halfway point of his [#permalink]

Show Tags

New post 22 Jan 2018, 22:25
You combine speed when you talk about relative speed. Two objects moving toward each other or away from each other etc. Check these two posts for concepts of relative speed:

https://www.veritasprep.com/blog/2012/0 ... elatively/
https://www.veritasprep.com/blog/2012/0 ... -concepts/
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for $199

Veritas Prep Reviews

Re: At what speed was Erik running when he was at the halfway point of his   [#permalink] 22 Jan 2018, 22:25
Display posts from previous: Sort by

At what speed was Erik running when he was at the halfway point of his

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


cron

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®.