Question

A boy goes from his house to school by bus at a speed of 20 kilometre per hour and returns back to the same route at a speed of 30 kilometre per hour the average speed of his Journeys

Answer 1

Let the distance between the school and the house is x km.

Speed of the boy from house to school

= 20 km/hr.

Now,

$time \: taken \: = \frac{distance}{speed} \\ \\ = \frac{x}{10} \: hr$

Also, Speed of the boy from school to the house = 30 km/hr

$So, \: time \: taken \: = \frac{x}{30} \: hr \\ \\ = > total \: \: time \: taken \: = \: \frac{x}{20} + \frac{x}{30} \\ \\ \: \: \: \: \: \: \: \: \: \: \: \: = \: \: \: \frac{x}{12} \: hr \\ \\ Also \: \: total \: distance \: covered \: \\ by</h3><h3> \: boy \: = x + x \: = 2x \: km \\ \\ Using \: formula, \\ \\ \: average \: speed \: = \frac{total \: distance}{total \: time} \\ \\ = \frac{2x}{ \frac{x}{12} } \\ \\ = \frac{2x \times 12}{x} \\ \\ = 24 \: km/hr.$

This is the required average speed.

I hope this helps.