Question
Thu February 26, 2009 By: Meher Dhingra

motion

Expert Reply
Thu February 26, 2009

Average speed = total distance / total time taken

Let the distance from arpit's home to school = S
The time taken while going to school= t1 = distance /speed = S/20
The time taken while returning from school= t2 = S/40

Total distance travelled in going and returning from school = 2S

Hence the average speed = 2S/[t1+t2] = 2S /[ S/20 + S/40] = 2 / [1/20 + 1/40 ]

Average speed = 26.6km/hr

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