Answer :

Given:

speed from a to b=30 km/h

speed from b to a=20 km/h

1.average speed

let distance from a to b be "D"

as we know

2. speed of an object

where

s is the speed of the object

d is the distance traveled by the object

t is the time taken by the object to travel distance D

putting the value of s a to b in equation 2

D=30 × T

_{1 (3)}

putting the value of s b to a in equation 2

D =20 × T

_{2 (4)using equation 3 and 4, we get }30 × T

_{1 }= 20 × T

_{2}

T

_{2 }= 1.5 × T

_{1}The total distance traveled by the body is D+D =2 × D

The total time taken by the body is T

_{1}+ T

_{2= }T

_{1 }+1.5×T

_{1}= 2.5 × T

_{1}putting the value in equation 1 , we get

The average speed of the object is 24 km/h

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