Question

A car travels 40 kilometers at an average speed of 80 km/h and then travels 40 kilometers at an average speed of 40 km/h. What is the average speed of the car for this 80 km trip?(1)40km/h

(2)45km/h

(3)48km/h

(4)53km/h

Answer 1

Given Data:

The total distance travelled is $\text{=80 km.}$

Half distance (40 km) is travelled at 80 km/h and the remaining half distance (40km) is travelled at 40 km/h.

Step 1: Time used:

FRom formula :$time\left(t\right)=\frac{Distance\left(d\right)}{speed\left(v\right)}$

Time taken to cover first 40km, $t=\frac{40}{80}=0.5h$

Time taken to cover next 40km, $t^{\prime }=\frac{40}{40}=1h$

Total time taken $t+t^{\prime }\text{= 1.5 hour}$ = 1.5 hour

Now,

$Averagespeed=\frac{totaldistance}{totaltimetaken}=\frac{80km}{1.5h}=53.33$ km/h

Answer : 53.33 km/h