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Speed/Distance/Time

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Speed/Distance/Time

by ssrege » Sat Feb 14, 2009 1:25 pm
Two dogsled teams raced across a 300 mile course in wyoming. Team A finished the course 3 hours fewer than did team B. If team A's average speed was 5 miles/hour greater than that of team B, what was team B's average speed in miles per hour?

A. 12
B. 15
C. 18
D. 20
E. 25

I am not able to solve this problem.
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by truplayer256 » Sat Feb 14, 2009 1:43 pm
I hope you know that average speed equals total distance/total time..

Let's say that it took Team B y hours and because of this, Team A took y-3 hours.

TOTAL DISTANCE= 300 Miles
TOTAL TIME: Team A=y-3
Team B=y
300/y-3=(300)/(y)+5
5y^2-15y-900=0
y=15
Team B's avg speed= 300/y=300/15=20 or D
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by cramya » Sat Feb 14, 2009 1:53 pm
Plug n play

Start with E i.e 25

B:
300/25 = 12

A:

300/30 = 10

NO

Then OPTION D I.E 20

B:
300/20=15

300/25 = 12

A finishing 3 hours fewer than B is met

Choose D)
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