Question

A car travels 400 km in the first 4.5 hours of a trip. It stops for an hour and then travels final 300 km in 2.5 hours. Find the average speed of the car.

Answer 1

Given data:

Distance traveled by car in t_1=4.5 hr is s_1=400 km.

Distance traveled by car in t_2=1 hr is s_2=0 km (as the car was stopped).

Distance traveled by car in t_3=2.5 hr is s_3=300 km.

The average speed is given as,

`\begin{gathered} v_(avg)=\frac{\text{ total distance traveled}}{\text{total time taken}} \\ =(s_1+s_2+s_3)/(t_1+t_2+t_3) \end{gathered}`

Substitute all known values,

`\begin{gathered} v_(avg)=\frac{(400\text{ km})+(0\text{ km})+(300\text{ km})}{(4.5\text{ hr})+(1\text{ hr})+(2.5\text{ hr})} \\ =87.5\text{ km/h} \end{gathered}`

Therefore, the average speed of the car is 87.5 km/h.