Physics

Problem

3. Abdul, while driving to school, computes the average speed for his trip to be

20 \mathrm{~km} \mathrm{~h}^{-1}

. On his return trip along the same route, there is less traffic and the average speed is

30 \mathrm{~km} \mathrm{~h}^{-1}

. What is the average speed for Abdul's trip?