Karan walks to his gymnasium which is at a distance of 5 km from his home in 20 minutes. On reaching he finds that the gymnasium is closed and comes back home on his friend’s bicycle in 10 minutes. His average speed for the whole journey is:

Average speed is the total distance covered in the given time.

Average speed =$\frac{\mathrm{Total} \mathrm{distance} \mathrm{covered}}{\mathrm{Total} \mathrm{time} \mathrm{taken}}$

Total distance=  5 + 5 = 10 km
Total time taken = 20 + 10 = 30 min = 0.5 hr

$\therefore$Average speed =$\frac{10}{{\displaystyle 0.5}}=20 \mathrm{km}/\mathrm{h}$

Therefore, Karan's average speed will be 20 km/h.