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Manhattan GMAT - Word Problem

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Manhattan GMAT - Word Problem

by Nee609 » Sat Apr 18, 2015 12:20 pm
Below question is from Manhattan GMAT book and I am not sure if the answer provided is correct or not.

Two racecar drivers, Abernathy and Berdoff, are driving around a circular track. If Abernathy is 200 meters behind Berdoff and both drivers drive at their respective constant rates, how long, in seconds, will it take for Abernathy to catch up to Berdoff?

(1) The circumference of the racetrack is 1,400 meters.
(2) Berdoff is driving 25 meters per minute faster than Abernathy.

Please advice how to solve this question.

Thanks in advance!
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by Brent@GMATPrepNow » Sat Apr 18, 2015 12:50 pm
You transcribed statement 2 incorrectly. It should read as follows:
Nee609 wrote: Two racecar drivers, Abernathy and Berdoff, are driving around a circular track. If Abernathy is 200 meters behind Berdoff and both drivers drive at their respective constant rates, how long, in seconds, will it take for Abernathy to catch up to Berdoff?

(1) The circumference of the racetrack is 1,400 meters.
(2) Abernathy is driving 25 meters per minute faster than Berdoff.

Target question: How long, in seconds, will it take for Abernathy to catch up to Berdoff?

Given: Abernathy is 200 meters behind Berdoff

Statement 1: The circumference of the racetrack is 1,400 meters.
The circumference of the racetrack is irrelevant here. What matters is their respective speeds.
For example, it could be that Abernathy and Berdoff are driving at the same speed, so Abernathy will NEVER catch up to Berdoff.
Of it could be the case that Abernathy's speed is 200 meters/second FASTER THAN Berdoff's speed, in which case, Abernathy will catch up to Berdoff in 1 second.
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: Abernathy is driving 25 meters per minute faster than Berdoff
If Abernathy is driving 25 meters per minute faster than Berdoff, then the GAP between Abernathy and Berdoff will DECREASE by 25 meters EVERY MINUTE.
There is currently as 200-meter gap
So, it will take 8 minutes to decrease the gap from 200 meters to 0 meters.
In other words, Abernathy will catch up to Berdoff in 8 minutes.
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer = B

Cheers,
Brent
Last edited by Brent@GMATPrepNow on Mon Apr 20, 2015 7:23 pm, edited 1 time in total.
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by Nee609 » Sat Apr 18, 2015 4:37 pm
Exactly, thats what i thought. Manhattan 5th Edition has it wrong. Cool, thanks for clearing that.
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by Matt@VeritasPrep » Sun Apr 19, 2015 11:07 pm
Of course, this is a circular track, so even if Berdoff is ahead AND going faster, they'll have to be side by side for a moment again eventually! (That isn't really "catching up", but hey ...)
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by Brent@GMATPrepNow » Mon Apr 20, 2015 5:57 am
I think the term you're looking for is "lapped" :-)

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by ceilidh.erickson » Mon Apr 20, 2015 11:30 am
Nee609 wrote:Exactly, thats what i thought. Manhattan 5th Edition has it wrong. Cool, thanks for clearing that.
You're right - sometimes things get mixed up on the way to the publisher! This is a known error that we fixed in our 6th edition guides.

If you ever think you've spotted another error, please check out our Errata page for the correction: https://www.manhattanprep.com/gmat/errata/
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
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by prada » Mon Apr 20, 2015 5:16 pm
Brent@GMATPrepNow wrote:You transcribed statement 2 incorrectly. It should read as follows:
Nee609 wrote: Two racecar drivers, Abernathy and Berdoff, are driving around a circular track. If Abernathy is 200 meters behind Berdoff and both drivers drive at their respective constant rates, how long, in seconds, will it take for Abernathy to catch up to Berdoff?

(1) The circumference of the racetrack is 1,400 meters.
(2) Abernathy is driving 25 meters per minute faster than Berdoff.

Target question: How long, in seconds, will it take for Abernathy to catch up to Berdoff?

Given: Abernathy is 200 meters behind Berdoff

Statement 1: The circumference of the racetrack is 1,400 meters.
The circumference of the racetrack is irrelevant here. What matters is their respective speeds.
For example, it could be that Abernathy and Berdoff are driving at the same speed, so Abernathy will NEVER catch up to Berdoff.
Of it could be the case that Abernathy's speed is 200 meters/second FASTER THAN Berdoff's speed, in which case, Abernathy will catch up to Berdoff in 1 second.
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: Abernathy is driving 25 meters per minute faster than Berdoff
If Abernathy is driving 25 meters per minute faster than Berdoff, then the GAP between Abernathy and Berdoff will DECREASE by 25 meters EVERY MINUTE.
There is currently as 200-meter gap
So, it will take 8 seconds to decrease the gap from 200 meters to 0 meters.
In other words, Abernathy will catch up to Berdoff in 8 seconds.
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer = B

Cheers,
Brent
Don't you mean 8 mins and not seconds? They question asks the answer in seconds so 60*8= 480 seconds.
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by Brent@GMATPrepNow » Mon Apr 20, 2015 7:24 pm
prada wrote: Don't you mean 8 mins and not seconds? They question asks the answer in seconds so 60*8= 480 seconds.
Good catch - I have edited my response accordingly.

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