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2 cars started at the same point and travelled a straight

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2 cars started at the same point and travelled a straight [#permalink] New post 08 Feb 2008, 05:41
2 cars started at the same point and travelled a straight course for 2 hrs in opposite direction at which they were 208 miles apart.if 1 travelled at an average 8 miles apart than the other what was the average speed of 2?
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Re: divergent rates [#permalink] New post 08 Feb 2008, 06:39
208=108+100

V=100miles/2h=50 miles/h

is it right?
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Re: divergent rates [#permalink] New post 08 Feb 2008, 12:56
Is this the question in its entirety?

Quote:
Two cars started from the same point and traveled on a straight course in opposite directions for exactly 2 hours, at which time they were 208 miles apart. If one car traveled, on average, 8 miles per hour faster than the other car, what was the average speed for each car for the 2-hour trip?


Two cars traveling for 2 hours apiece go 208 miles. In other words, 4 hours of total driving = 208 miles. 208/4 = 52 mph average for both cars.

If one car was going 8mph faster than the other car and we want to find out each cars average just find the two speeds that are 8mph and average at 52. In this case (52+4) and (52-4) or 56mph and 48 mph.

Double-check answer:
48(2)+56(2) = 96+112 = 208 miles
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Re: divergent rates [#permalink] New post 08 Feb 2008, 13:10
bmwhype2 wrote:
2 cars started at the same point and travelled a straight course for 2 hrs in opposite direction at which they were 208 miles apart.if 1 travelled at an average 8 miles apart than the other what was the average speed of 2?


R r+8 r
T 2 2
D d 208-d


2r=208-(2r+16) --> 4r= 192 --> r=48 (made the mistake earlier of have 4r=224 stupid minus sign!)

so answer is 48
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Re: divergent rates [#permalink] New post 08 Feb 2008, 14:36
I got 52 as the answer.

Assumie one car travels x km in 2 hours and the other travles y in 2 hours.

total distance the two cars are apart:
x+y=208

Difference in the two speeds:
x/2-y/2=8

Sovling the above 2 linear equations:
x=112, y=96

Speed of first car: 112/2=56
Speed of second car:96/2=48

Average speeds of the two cars: (56+ 48)/2=52

Thus, the answer is 52.
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Re: divergent rates [#permalink] New post 08 Feb 2008, 18:32
eschn3am wrote:
Is this the question in its entirety?

Quote:
Two cars started from the same point and traveled on a straight course in opposite directions for exactly 2 hours, at which time they were 208 miles apart. If one car traveled, on average, 8 miles per hour faster than the other car, what was the average speed for each car for the 2-hour trip?


Two cars traveling for 2 hours apiece go 208 miles. In other words, 4 hours of total driving = 208 miles. 208/4 = 52 mph average for both cars.

If one car was going 8mph faster than the other car and we want to find out each cars average just find the two speeds that are 8mph and average at 52. In this case (52+4) and (52-4) or 56mph and 48 mph.

Double-check answer:
48(2)+56(2) = 96+112 = 208 miles


hrmmm wait what is the actual question? If this is the question then yes I say (56+48)/2 --> 52
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Re: divergent rates [#permalink] New post 08 Feb 2008, 19:35
GMATBLACKBELT wrote:
eschn3am wrote:
Is this the question in its entirety?

Quote:
Two cars started from the same point and traveled on a straight course in opposite directions for exactly 2 hours, at which time they were 208 miles apart. If one car traveled, on average, 8 miles per hour faster than the other car, what was the average speed for each car for the 2-hour trip?


Two cars traveling for 2 hours apiece go 208 miles. In other words, 4 hours of total driving = 208 miles. 208/4 = 52 mph average for both cars.

If one car was going 8mph faster than the other car and we want to find out each cars average just find the two speeds that are 8mph and average at 52. In this case (52+4) and (52-4) or 56mph and 48 mph.

Double-check answer:
48(2)+56(2) = 96+112 = 208 miles


hrmmm wait what is the actual question? If this is the question then yes I say (56+48)/2 --> 52



even if the question is asking for the average speed of one of the two cars you can use this approach to solve
Re: divergent rates   [#permalink] 08 Feb 2008, 19:35
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