Question

Abdul while driving to school computes the average speed for his trip to be 20 km/h. On his return trip along the same route there is less traffic and average speed is 30 km/h. What is the average speed for Abdul's whole trip?

Answer 1

Step 1: Given data

Average speed while driving to school = 20 km/h

Average speed while driving from school = 30 km/h

We have to find the average speed for the whole trip

Step 2: Calculation of the average speed of Abdul:

Let the distance between school and home of Abdul be X km.

Now,

Time to reach the school = t1=Distance/Speed=X/20 h

Time to reach from the school to home = t2=Distance/Speed=X/30 h

We know,

Averagespeed=Totaldistance/Totaltime

Putting all the values

Averagespeed=$\frac{2X}{\left({\displaystyle \frac{X}{20}}+{\displaystyle \frac{X}{30}}\right)}$

Averagespeed=$\frac{2X}{\left({\displaystyle \frac{3X+2X}{60}}\right)}$

Averagespeed=2X / (5X/60)

Averagespeed=(2×60)/5

Averagespeed=2×12

Averagespeed=24kmh^-1

Hence

The average speed of Abdul is 24 km/h.