Richa travels from A to B at the speed of 15 km/h, from B to C at 20 km/h, and from C to D at 30 km/h. If AB = BC = CD, then find the Richa's average speed.

Answer: Option D

Solution

Answer: Option D

Solution:

$$\begin{array}{rl}& \text{Distance}=\text{ LCM of }15,20,30=60\text{ km}\\ & \text{Average speed}=\frac{\text{Total distance}}{\text{Total time}}\\ & =\frac{3\times 60}{4+3+2}\\ & =\frac{180}{9}\\ & =\boxed{20\text{ km/h}}\end{array}$$