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 hl. What is the average speed for Abdul's trip?
Answers
Answer:
Average speed is 60km/hr
Explanation:
Given,
Speed taken to travel from your house to school is 20km/hr
Speed taken to travel from school to your house is 30km/hr
Now,
Lets Suppose the distance from your house to school is 'd'
Let suppose the time taken to travel from your house to school is t1 and time taken to travel from school to your house is t2
So,
t1=(d/20)hr
t2=(d/30)hr
As per question,
Average speed=d+d/t1+t2
. =2d/(d/20+d/30)
. =2d/d(1/20+1/30)
. =2/(50/600)
. =60km/hr
Formula used,
Time=Distance/Speed
Average speed= Total distance/Total time
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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