Multiple choice

A train traveled at a speed of 35 km./hr. for the first 10 minutes and at a speed of 20 km./hr. for the next 5 minutes. The average speed of the train for the total 15 minutes is -

  1. 30 km./hr.

  2. 23 km./hr.

  3. 31 km./hr.

  4. 29 km./hr.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Total distance = 35 × (10/60) + 20 × (5/60) = 350/60 + 100/60 = 450/60 = 7.5 km. Total time = 15 minutes = 0.25 hours. Average speed = 7.5/0.25 = 30 km/hr. This equals (35×10 + 20×5)/(10+5) = 450/15 = 30.

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