Question

I travelled at a speed of 600km/hour from chennai to coimbatore and returned at a speed of 800km/hour . Find my average speed

Answer 1

Average speed = {(600 + 800)/2} km/hr
= (1400/2) km/hr
= 700 km/hr

Answer 2

Let the distance travelled be x.
Total distance = 2x

Total time=
$\frac{x}{600} + \frac{x}{800} \\ \frac{4x + 3x}{2400} \\ \frac{7x}{2400}$
Now,
Since we know that,
$average \: speed = \frac{total \: distance}{totat \: time}$
So,
$average \: speed = \frac{2x}{ \frac{7x}{2400} }$
$\frac{2x \times 2400}{7x}$
$x = \frac{4800}{7} = 685 \frac{5}{7}$