Question

A car travels along a straight line for first half time with speed 40km/hr and the second half time with speed 60km/hr .find the average speed of car.

Answer 1

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Answer 2

The average speed of the car = 50 km/hr.

The car travels straight path for first half time and second half time. The average speed for the travel journey is calculated over total distance travelled and total time for the travel.

Given, speed1 = 40 km/hr and speed 2 = 60 km/hr.

Let us assume that the total time taken for the travel be x.

So, we have, distance travelled in first half be, $d 1=\text { speed } 1 \times {time 1}$

Time taken for first half be time1 = half of total time

$Time1=\frac{x}{2}$.

$\begin{aligned} \mathrm{d} 1 &=40 \times\left(\frac{x}{2}\right) \\ d 1 &=20 x \end{aligned}$

And, distance travelled in second half be, $\mathrm{d} 2=\text { speed } 2 \times \text { time } 2$

Time taken for second half be time2 = half of total time

$Time2=\frac{x}{2} m.$

$\begin{array}{l}{\mathrm{d} 2=60 \times\left(\frac{x}{2}\right)} \\ {\mathrm{d} 2=30 x}\end{array}$

Thereby, Average speed = total distance / total time

Total distance $\begin{array}{l}{=d 1+d 2} \\ {=20 x+30 x} \\ {=50 x}\end{array}$                                                          

Total time = x

Average speed $\begin{array}{l}{=\frac{50 x}{x}} \\ {=50 \mathrm{km} / \mathrm{hr}}\end{array}$.