Question

a car travels at speed of 80km/h during the first half of its running and time and at 40km/h during the other half.find the average speed of a car 60km/h​

Answer 1

For first half, distance=v1t/2.........for second half, distance=v2t/2

Average speed=v1t/2+v2t/2 the whole divided by t/2+t/2

                    =v1t+v2t/2/t

                    =v1+v2/2

 

                      80+40/2 = 60 km/h  

 

Answer 2

Given

A car travels at a speed of 80 km/h during the first half of its running time and at 40 km/h during the other half

To Find

The average speed of the car

Solution

We know that

$\rm \longrightarrow v_{avg}=\dfrac{v_{1}+v_{2}}{2}$

According to the question

We are asked to find the average speed of the car

Therefore

We must find $\rm "v_{avg}"$

Given that

A car travels at a speed of 80 km/h during the first half of its running time and at 40 km/h during the other half

Hence

• $\rm v_{1}$ = 80 km/h
• $\rm v_{2}$ = 40 km/h

Substituting the values

We get

$\rm \longrightarrow v_{avg}=\dfrac{80+40}{2} \ km/h$

$\rm \longrightarrow v_{avg}=\dfrac{120}{2} \ km/h$

Therefore

$\rm \longrightarrow v_{avg}=60 \ km/h$

Hence

The average speed of the car = 60 km/h