Dave made a 90-mile sales trip. For the first half of the distance, he averaged 45 miles per hour. For the last half, he drove 60 miles per hour. What was his total time, in hours, for the trip?
The total length of the trip was 90 miles, so the first and second halves were each 45 miles. Use the formula t = d ÷ r to find his time for each half of the trip.