Elijah drove 45 miles to his job in an hour and ten minutes in the morning. On the way home in the evening, however, traffic was much heavier and the same trip took an hour and a half. What was his average speed in miles per hour for the round trip?

To determine this, first determine the total distance of the round trip. This is twice the 45 miles of the one-way trip to work in the morning, or 90 miles. Then, to determine the total amount of time Elijah spent on the round trip, first convert his travel times into minutes. One hour and ten minutes equals 70 minutes, and an hour and a half equals 90 minutes. So, Elijah’s total travel time was 70 + 90 = 160 minutes. Elijah’s average speed can now be determined in miles per minute:
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Finally, to convert this average speed to miles per hour, multiply by 60, since there are 60 minutes in an hour: Average speed (mph) = 60 × 0.5625 = 33.75 miles per hour.