Question

Sohail cycles on a circular track in anticlockwise direction. He travels with a speed ‘V’ to cover the path AB, next with speed ‘2V’ from B to C and with a speed of ‘3V’ from C to A. What is his average speed for the total journey? (AB = BC = CA)
$\left[3Marks\right]$

Answer 1

Let the circumference of the circle = 3d

the distance AB = BC = CA = d

$time=\frac{distance}{speed}$
$\left[1Mark\right]$

so, the time taken to cover $AC$ is $t_1=\frac{d}{V}$.
The time taken to cover $BC$ is $t_2=\frac{d}{2V}$.
The time taken to cover $CA$ is $t_3=\frac{d}{3V}$.
$\left[1Mark\right]$

Therefore, the average Speed is
$=\frac{3d}{\frac{d}{v}+\frac{d}{2v}+\frac{d}{3v}}$

$=\frac{3d}{\frac{d\times (6+3+2)}{6V}}=\frac{3\times 6V}{11}=\frac{18V}{11}$
$\left[1Mark\right]$