Multiple choice

Mark drove a certain distance to his friend's house at a speed of 30 mph and returned home at a speed of 20 mph. The round trip took him 4 hours and 30 minutes. How far away does his friend live?

  1. 27 miles

  2. 34 miles

  3. 44 miles

  4. 54 miles

  5. 108 miles
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let distance be d. Time = d/30 + d/20 = 4.5. (2d + 3d) / 60 = 4.5. 5d / 60 = 4.5. d/12 = 4.5. d = 54.

AI explanation

Use the harmonic mean formula for equal distances, where average speed equals (2 multiplied by 30 multiplied by 20) divided by (30 + 20), giving 24 mph. The total time for the round trip is 4.5 hours, so the total distance is 24 multiplied by 4.5, which equals 108 miles. Since this is a round trip, the distance to the friend's house is half of 108, resulting in 54 miles.

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