Tenzin drives from Gangtok to a hill town at 40 km/h and returns along the same road at 60 km/h. What is his average speed for the whole round trip?

Explanation

1. 01

   For equal distances at speeds $x$ and $y$, average speed $= \frac{2xy}{x+y}$.

2. 02

   $\frac{2 \times 40 \times 60}{40 + 60} = \frac{4800}{100} = 48$ km/h.