Multiple choice

David travels a distance of 60 km at the speed of 30 km/hr and then an additional 60 km at the speed of 50 km/hr. What is his average speed?

  1. 32.6 km/hr

  2. 37.5 km/hr

  3. 40 km/hr

  4. 42 km/hr
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B Correct answer
Explanation

Average speed is total distance divided by total time. Total distance = 60 + 60 = 120 km. Time 1 = 60/30 = 2 hours; Time 2 = 60/50 = 1.2 hours. Average speed = 120 / 3.2 = 37.5 km/hr.

AI explanation

Using the harmonic mean formula for equal distances, Average Speed = (2 multiplied by S1 multiplied by S2) / (S1 + S2). Substituting the values gives (2 multiplied by 30 multiplied by 50) / (30 + 50), equaling 3000 / 80. This calculates to 37.5 km/hr, giving the result 37.5 km/hr.

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