Multiple choice

The distance between City A and City B is 140 miles. Danny starts driving from City A to City B at 3:00 PM and travels at 70 mph. He spends 20 minutes in City B. At what speed should he drive while coming back, if he needs to come back to City A at exactly 7:00 PM?

  1. 66 mph

  2. 75 mph

  3. 80 mph

  4. 84 mph

  5. 90 mph
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Distance is 140 miles. Outbound time = 140/70 = 2 hours. He arrives at 5:00 PM, stays 20 mins, leaves at 5:20 PM. He needs to return by 7:00 PM, so he has 1 hour and 40 minutes (100 minutes = 5/3 hours). Speed = 140 / (5/3) = 140 * 3 / 5 = 84 mph.

AI explanation

The total time from 3:00 PM to 7:00 PM is 4 hours. Danny spends 20 minutes, which is 1 by 3 of an hour, in City B, leaving 3 and 2 by 3 hours for total driving. Since the one-way distance is 140 miles and he travels at 70 mph, the journey to City B takes 2 hours, leaving 1 and 2 by 3 hours for the return trip. Using the formula Speed equals Distance divided by Time, the required return speed is 140 miles divided by 5 by 3 hours, which equals 84 mph. He should drive at 84 mph.

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