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A motorcyclist drives from A to B with a uniform speed of 30 km h–1 and returns back with a speed of 20 km h–1. Find its average speed. - Science

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Question

A motorcyclist drives from A to B with a uniform speed of 30 km h–1 and returns back with a speed of 20 km h–1. Find its average speed.

Answer in Brief

Solution

Let the distance between A and B be S km.

Time taken in going from A to B = `"s"/30 "h"`

Time taken in going from B to A = `"s"/20 "h"`

Average speed of motorcyclist = `"total distance covered"/"total time taken"`

= `("S km" + "S km")/("S"/30"h" + "S"/20"h")`

= `2/(1/30 + 1/20) "km h^-1"`

= `2/(1/12) "km h"^-1`

= 24 km h−1

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Chapter 8: Motion - Short Answer Questions [Page 59]

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NCERT Exemplar Science [English] Class 9
Chapter 8 Motion
Short Answer Questions | Q 16. | Page 59

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