Question

If Suresh travels $\frac{1}{3}$rd of a certain distance by car at the speed of 60 km/hr and the rest of the distance by bike at the speed of 30 km/hr, then find his average speed for the whole journey.

• A. 45 km/hr
• B. 50 km/hr
• C. 36 km/hr
• D. 40 km/hr

Answer 1

The correct option is C 36 km/hr

Let the total distance covered by Suresh be 3D km.

So, time taken to travel$\frac{1}{3}$rd of the distance =$\frac{D}{60}$hours

Time taken to travel remaining $\frac{2}{3}$rd of the distance $\frac{2D}{30}$

Total time taken to travel 3D km$=\frac{D}{60}+\frac{2D}{30}=\frac{D}{12}$ hours.

Required average speed= $\frac{TotalDistance}{Totaltimetaken}=\frac{3D}{\frac{D}{12}}=3\times 12=36km/hr.$

Hence, option C is the correct answer.