Question

A motorcyclist drives from a to b with a uniform speed of 30 km /hr and returns with 20km/hr .Find his average speed

Answer 1

Answer:

Average speed of the motorcyclist

= 24 km/h

Step by step explanations :

given that,

A motorcyclist drives from A to B

with a uniform speed of 30 km /h

and returns with 20km/hr .

let the distance between A and B be d

here,

time taken to cover d from A to B

= d/30 h

and,

time taken to cover d from B to A

= d/20 h

now,

Average speed =

total distance travelled/total time taken

here,

total distance travelled = 2d

[from A to B and then from B to A]

total time taken = d/30 + d/20

= (3d + 2d)/60

= 5d/60

= d/12 h

now average speed

= 2d/(d/12)

= 24d/d

= 24 km/h

so,

Average speed of the motorcyclist

= 24 km/h

Answer 2

Answer:

Average speed of the motorcyclist

= 24 km/h

Step by step explanations :

let the distance between A and B be s,

now,

time taken to while going from A to B

= s/30 h,

time taken to in in returning = s/20 h

now,

Average speed =

total distance travelled/total time taken

= 2s/(s/30 + s/20)

= 120s/5s

= 24

Average speed = 24 km/h