Question

If speed is 20km/hr in first half of journey and 30km/hr in second half of journey. Find average speed

Answer 1

Answer:

Average speed of journey is 24 km/hr

Explanation:

let total distance covered is x

let x/2 distance cover in time t1 with speed of 20 km/hr

and  x/2 distance cover in time t2 with speed of 30 km/hr

$t_{1} =Distance/speed =\frac{0.5x}{20} \\t_{2} = \frac{0.5x}{30}$

Total time of travel is

$t_{1}+t_{2}=\frac{0.5x}{20} +\frac{0.5x}{30}\\t_{1}+t_{2}=\frac{1.5x+x}{60} \\t_{1}+t_{2}=\frac{2.5x}{60} \\t_{1}+t_{2}=\frac{x}{24}$

Average speed is = $total distance /total time$

=x/(x/24)

=24 km /hr

Average speed of journey is 24 km/hr