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Motion Problem!!

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Motion Problem!!

by Ozlemg » Sat Jul 30, 2011 12:04 pm
Car A and Car B are both travelling in the same direction along the same route. And Car A is 50 miles behind Car B. Car A is travelling at a cosntant rate of 60 miles per hour and Car B is 52 miles per hour. Approximately how many hours will it take for Car A to overtake Car B and drive 16 miles ahead of Car B?

. 6
.10
.16
.18
.20

OA to follow!
Last edited by Ozlemg on Mon Aug 01, 2011 1:02 am, edited 1 time in total.
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by Jim@Knewton » Sat Jul 30, 2011 12:47 pm
Source of Q? All details correct?

1. Diff of speed = 8 mph, diff of distance = 50+16 =66 miles, => time taken = 66/8 = 8.25 hours

2. D = speed *time, let time =t, then D= 52t for B and D+50+16 = 60t for A
=> 8t = 66, so t=8.25

3. Every hour A gains 8 miles on B => For given answer choices in hours:
. 6 ----> 8*6 = 48 => in 6 hours A will be 2 miles behind B
.10 ----> 8*10 =80 => in 10 hours A will be 30 miles ahead of B
.16 = A will be 78 miles ahead
.18 = A will be 94 miles ahead
.20 = A will be 110 miles ahead

So what's happening here :-) ?
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by MarkMeier20 » Sat Jul 30, 2011 12:49 pm
Go into the rest frame of car B:
In this rest frame the speed of car B is zero, the speed of car A is 8 miles/ hour

How long does car A need to travel 50+16=66 miles?

Answer: 66/8=8,25h
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by BlindVision » Sat Jul 30, 2011 3:19 pm
Ozlemg wrote:Car A and Car B are both travelling in the same direction along the same route. And Car A is 50 miles behind Car B. Car A is travelling at a cosntant rate of 60 miles per hour and Car B is 52 miles per hour. How many hours will it take for Car A to overtake Car B and drive 16 miles ahead of Car B?

. 6
.10
.16
.18
.20

OA to follow!
Car A is traveling 8 miles per hour faster than Car B. Each hour, Car A is 8 miles ahead of Car B.

Car A needs to make up 50 miles + 16 miles = 66 miles

66 miles / 8 miles per hour

= 8.25 hours

rounded to Choice B
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by GmatKiss » Mon Aug 01, 2011 6:10 am
from the given, the series goes as,

car B: 102,154,206,258,310,362,424,476,528,580
car A: 60,120,180,240,300,360,420,480,520,600

almost 10 hours!!

IMO:B
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