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average speed

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average speed

by [email protected] » Fri Jan 02, 2009 2:41 pm
13. The time it took car A to travel 400 miles was 2 hours less than the time it took car B to travel the same distance. If car A’s average speed was 10 miles per hour greater than that of car B, what was car B’s average speed, in miles per hour?
(A) 20
(B) 30
(C) 40
(D) 50
(E) 80
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by cramya » Fri Jan 02, 2009 2:46 pm
U can solve it algebrically but the quickest way would be to plug in numbers and eliminate

Start with C) since A and B are lesser than that . D) AND E) greater

B's speed 40

400/40 = 10 hours

A's speed

400/50 = 8

Done choose C)

Even if u had to plug in 2 more numbers still its a lot quicker.Just my opinion
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Re: average speed

by logitech » Fri Jan 02, 2009 2:49 pm
13. The time it took car A to travel 400 miles was 2 hours less than the time it took car B to travel the same distance. If car A’s average speed was 10 miles per hour greater than that of car B, what was car B’s average speed, in miles per hour?

A’s average speed was 10 miles per hour greater than that of car B

(A) 20 - 30
(B) 30 - 40
(C) 40 - 50 (400/40 = 10 400/50 = 8 ; 10 -8 -2 )
(D) 50 - 60
(E) 80 - 90

or

400/V - 400/(v+10) =2

And V = 40
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