A bus travels first $60$ km at $30$ km/h and the next $60$ km at $60$ km/h. Its average speed for the whole…

A bus travels first $60$ km at $30$ km/h and the next $60$ km at $60$ km/h. Its average speed for the whole journey is:
  1. $40$ km/h
  2. $45$ km/h
  3. $48$ km/h
  4. $50$ km/h

Solution

Time $= \dfrac{60}{30} + \dfrac{60}{60} = 2 + 1 = 3$ hr. Total distance $= 120$. Average $= \dfrac{120}{3} = 40$ km/h.

Asked in: IMO

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