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Shrinking Distance Between Travelers on Kiss and Quarrel

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afashoro
 Post subject: Shrinking Distance Between Travelers on Kiss and Quarrel
 Post Posted: Thu Sep 09, 2010 12:54 am 
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Posts: 7
Conceptually I'm having a hard time fully grasping why it makes sense to add the rates together (assuming the travelers are moving simultaneously) in order to find the rate of the shrinking/growing distance between travelers.
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chitrangada.maitra
 Post subject: Re: Shrinking Distance Between Travelers on Kiss and Quarrel
 Post Posted: Thu Sep 09, 2010 3:00 pm 
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Course Students


Posts: 75
Hi,

The rates are added only if both these criteria are met.

1. the objects are moving simultaneously
2. the objects are moving towards each other

Lets say a man is walking towards a coffee shop, 10 km away at a speed of 5 km/hr. It will take him 2 hours to reach the coffee shop.

What we did here is distance / speed or 10/5=2

Again, lets say the coffee shop decides to move towards the man (wild, I know). Starting distance between the man and the coffee shop is the same i.e. 10 km. Lets say the coffee shop is walking towards the man at 5km/hr.
So, the time it takes for the man to get his coffee should be less because now two people are making the effort of walking.

It will take them 1 hour to meet.
What we did here is 10/5+5=1

distance/speed of man+speed of coffee shop.

Hope that helps,
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afashoro
 Post subject: Re: Shrinking Distance Between Travelers on Kiss and Quarrel
 Post Posted: Thu Sep 16, 2010 2:35 am 
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Course Students


Posts: 7
Hi,

Thank you very much. This helps a lot conceptually.

Thank you again for taking time to answer.
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tim
 Post subject: Re: Shrinking Distance Between Travelers on Kiss and Quarrel
 Post Posted: Mon Sep 20, 2010 8:08 pm 
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ManhattanGMAT Staff


Posts: 1779
Location: Southwest Airlines, seat 21C
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