SOLUTION: dave could drive 300 miles in twice the time in took john to drive 240 miles. The speed of john was 30 mph greater than that of dave. What were the speeds and times of both?

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Question 470595: dave could drive 300 miles in twice the time in took john to drive 240 miles. The speed of john was 30 mph greater than that of dave. What were the speeds and times of both?
Answer by lwsshak3(11628) About Me  (Show Source):
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dave could drive 300 miles in twice the time in took john to drive 240 miles. The speed of john was 30 mph greater than that of dave. What were the speeds and times of both
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let x=dave's speed
x+30=john's speed
travel time=distance/speed
dave's travel time=300/x
john's travel time=240/(x+30)
300/x=2*240/(x+30)
300/x=480/(x+30)
cross-multiply
300(x+30)=480x
300x+9000=480x
180x=9000
x=50
ans:
dave's speed=50 mph
john's speed=50+30=80 mph