Question

3. 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 the average speed is
30 km h, What is the average speed for Abdul's trip?​

Answer 1

Answer:

24 km/h

Explanation:

Given:

Speed while driving to school = 20 km/h

speed while coming back from school = 30 km/h

let total distance = X

To find:

Average speed

Average speed$=\frac{Total \ distance }{Total \ time}$

Total distance = X+X = 2X (Abdul goes and also returns back from school)

$Time = \frac{distance}{speed}$

So time while going to school = $\frac{x}{20}$

Time while coming back from school = $\frac{x}{30}$

So, substituting these values, we get:

$= \frac{2x}{\frac{x}{20}+\frac{x}{30} }$

$=\frac{2x}{\frac{3x}{60}+\frac{2x}{60} }$

$=\frac{2x}{\frac{5x}{60} }$

$=\frac{2x}{5x} \times 60$

$= \frac{2}{5} \times 60$

$= 2 \times 12$

$= 24 km/h$

The average speed for abdul's trip is equal to 24 km/h

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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