Abdul, while driving to school, computes the average speed for his trip to be 20 km h-1. On his return trip along the same route, there is less traffic and the average speed is 30 km h-1. What is the average speed for Abdul's trip?

Given that

Abdul, while driving to school, computes the average speed for his trip to be 20 km h-1. On his return trip along the same route, there is less traffic and the average speed is 30 km h-1.

We need to find

The average speed for Abdul’s trip

Solution

Let us take the following assumptions for calculating the average speed for Abdul’s trip

As per given data in the question

Average speed from home to school v1av = 20km h-1
Average speed from School to Home v2av = 30km h-1

Our assumptions

The distance Abdul commutes while driving from Home to School = s
Let us assume time taken by Abdul to commutes this distance = t1
Distance Abdul commutes while driving from School to Home = S
Let us assume time taken by Abdul to commutes this distance = t2

Also we know that

The time taken from Home to School t1=S/v1av
Similarly Time taken from School to Home t2=S/v2av

Total distance

Total distance from home to school and backward = 2S——-(i)

Total time taken from home to school and backward (T)=S/20+S/30———-(ii)

Formula

Speed = Distance  / Time

Therefore,

Average Speed(Vav)for covering total distance (2s)=Total Distance/Total Time

So from equations (i)  and (ii) we get,
Average Speed(Vav) =2S/(S/20+S/30)
=2S/[30S+20S)/600] =1200S/50S
=24kmh-1

Final Answer

The average speed for Abdul’s trip = 24kmh-1

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