Question

A car travels $30km$ at a uniform speed of $40km/h$ and the next $30km$ at a uniform speed of $20km/h$. Find its average speed.

Answer 1

Step 1, Given data

Speed = 40 km/h, Distance = 30 km

Speed = 20 km/h, Distance = 30 km

Step 2, Finding the average speed

For the first part

Time = $\frac{Distance}{Speed}=\frac{30}{40}=\frac{3}{4}$ h

For the second part

Time = $\frac{Distance}{Speed}=\frac{30}{20}=\frac{3}{2}$ h

Now,

$Averagespeed=\frac{Totaldistancetraveled}{Totaltimetaken}=\frac{60}{\frac{3}{4}+\frac{3}{2}}$

After solving

Average speed = $\frac{80}{3}$ km/h