I am having trouble with distance calculation (2)

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candygal79: Senior | Next Rank: 100 Posts; Posts: 49; Joined: Mon Feb 10, 2014 1:18 amFollowed by: 3 members

by candygal79 » Wed Mar 19, 2014 8:33 pm

Two cars travel away from each other in opposite directions at 24 miles per hour and 40 miles per hour respectively. If the first car travels for 20 mins and the second car for 45 min, how many miles apart will they be at the end of their trips ?

22

24

30

38

42

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theCodeToGMAT: Legendary Member; Posts: 1556; Joined: Tue Aug 14, 2012 11:18 pmFollowed by: 34 members; Thanked: 448 times; GMAT Score:650

by theCodeToGMAT » Wed Mar 19, 2014 8:56 pm

Speed = 24 & 40

Time of first car = 20 mins = 1/3 hr

TIme of Second Car = 45min = 3/4 hr

Distance travelled by first car = 24 * 1/3 = 8 miles

Distance travelled by second car = 40 * 3/4 = 30 miles

Total Gap = 30+8 = 38 miles

R A H U L

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QuantVeda: Newbie | Next Rank: 10 Posts; Posts: 4; Joined: Wed Mar 19, 2014 10:36 pm

by QuantVeda » Wed Mar 19, 2014 10:56 pm

To get this question right, you have to visualize the problem. In this problem, both cars is at a point and are moving in opposite direction i.e. if first car moves towards east from initial point, second car moves towards west from the same initial point.once you visualize the problem, you will realize that distance when they stopped their journey will be the SUM of the distance traveled by them. The distance between them will be given by

24 miles/hr X (20/60)hr +40 miles/hr X(45/60)hr
8 miles + 30 miles = 38 miles

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GMATGuruNY: GMAT Instructor; Posts: 15539; Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members; Location: New York, NY; Thanked: 13060 times; GMAT Score:790

by GMATGuruNY » Thu Mar 20, 2014 5:03 am

Two cars travel away from each other in opposite directions at 24 miles per hour and 40 miles per hour respectively. If the first car travels for 20 mins and the second car for 45 min, how many miles apart will they be at the end of their trips ?

22

24

30

38

42

<-----Car A-----X-----Car B----->

Let X = the starting point for both cars.

RED distance:
This distance is traveled by Car A at speed of 24 mph.
Since the time is 20 minutes -- the equivalent of 1/3 of an hour -- we get:
Red distance = r*t = (24)(1/3) = 8 miles.

BLUE distance:
This distance is traveled by Car B at speed of 40 mph.
Since the time is 45 minutes -- the equivalent of 3/4 of an hour -- we get:
Blue distance = r*t = (40)(3/4) = 30 miles.

Total distance between the 2 cars:
Red distance + blue distance = 8+30 = 38 miles.

The correct answer is D.

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Abhishek009: Master | Next Rank: 500 Posts; Posts: 359; Joined: Wed Mar 11, 2009 4:37 amFollowed by: 2 members; Location: Kolkata, India; Thanked: 50 times

by Abhishek009 » Thu Mar 20, 2014 6:58 am

candygal79 wrote:Two cars travel away from each other in opposite directions at 24 miles per hour and 40 miles per hour respectively. If the first car travels for 20 mins and the second car for 45 min, how many miles apart will they be at the end of their trips ?

||======================A | B==========================||

candygal79 wrote:If the first car travels for 20 mins

Distance covered by car A is 20 Minutes is = 1/3 * 24 => 8 miles

||==================8 Miles===============A | B

candygal79 wrote:The second car for 45 min, how many miles apart will they be at the end of their trips ?

Distance covered by car B is 20 Minutes is = 45/60 * 40 => 3/4 * 40 => 30 miles.

A | B==================30 Miles=====================||

So the complete Picture stands as -

||==========8 Miles==========A | B==========30 Miles===========||

So , The two Cars are 38 Miles apart.

Hope this helps you to some extent.

Abhishek

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