Question

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

Answer 1

Explanation:

here x = 20km/hr

and y = 30km/hr

average speed = 2xy/x + y

= ( 2 × 20 × 30 )/20 + 30

= 1200/50

= 24

the average speed of Abdul is 24kmph

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Answer 2

Correct Question -

Abdul while driving to school computes the average speed of the trip to be 20 kmph .

On his return trip along the same route , there is less traffic and the average speed is 30 kmph .

What is the average speed for Abdul ' s trip ?

Solution -

See the attached diagram ....

In the above Question , the following information is given -

Abdul while driving to school computes the average speed of the trip to be 20 kmph .

On his return trip along the same route , there is less traffic and the average speed is 30 kmph .

So ,

The innitial average speed is 20 kmph .

The final average speed is 30 kmph .

Let the distance between Abdul ' s home and his school be D metres .

Total distance covered by Abdul = 2 D

We also know the following formula -

Speed = [ Total Distance Covered ] / [ Total time taken ]

So ,

20 = [ D ] / [ T 1 ]

=> T 1 = [ D ] / 20

30 = [ D] / [ T 2 ]

=> T2 = [ D ] / 30

Total time taken for the whole trip

=> T 1 + T 2

=> D / 20 + D / 30

=> ( 5 D ) / 60

Now , Similarly -

Average Speed = [ Total Distance Covered ] / [ Total time taken ]

=> Average speed

=> [ 2 D ] / [ ( 5 D / 60 )

=> 24 kmph .

Hence the average speed for Abdul ' s trip is 24 kmph ...

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