SOLUTION: A driver sets out on a 20-mile trip. When he has gone halfway he finds he has averaged 25 mph. At what speed must he travel the rest of the way to make his overall average speed fo

Question 958255: A driver sets out on a 20-mile trip. When he has gone halfway he finds he has averaged 25 mph. At what speed must he travel the rest of the way to make his overall average speed for the trip 40 mph?
Answer by macston(5194) (Show Source): You can put this solution on YOUR website!
10 mi/25mph=0.4hr He has spent 0.4 hr going 10 miles
20mi/40mph=0.5hr To make the 20 mile trip at an average of 40 mph, he must complete the trip in 0.5 hour. He has already used 0.4 hour, so he must travel the last 10 miles in 0.1hr
10 miles/0.1hr= 100 miles per hour.
ANSWER: He must complete the trip at 100mph to average 40 mph for the whole trip.

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