Question

3
Abdul, while driving to school, computes the average speed for
route, there is less traffic and the average speed is
his trip to be 20 km h'. On his return trip along the same
PS
30 km h! What is the average speed for Abdul's trip?
lake accelerates​

Answer 1

Let x be the distance of the school and the time to reach the school =t1

Then ,

$t1 = \frac{Distance}{average \: speed} = \frac{x}{20}$

and the time taken in return trip ,t2

$t2 = \frac{distance}{average \: speed} = \frac{x}{30}$

$total \: time \: taken \: = t1 + t2 = \frac{x}{20} + \frac{x}{30} = \frac{x}{12}$

$and \: total \: distance = x + x = 2x$

$\therefore \: = average \: speed \: = \frac{total \: distance}{total \: time} = \frac{2x}{ \frac{x}{12} } = 24km {h}^{ - 1}$