Question

A car travels the first third of a distance with a speed of 10kmph, the second third at 20kmph and the last third of 60 kmph. what is its mean speed over the entire distance?

Answer 1

ANSWER

Let the total distance traveled be s.

Hence the time taken for first third of the distance= t

1

=

v

1

s/3

Similarly, the time taken for second third of the distance= t

2

=

v

2

s/3

and the time taken for last third of the distance= t

3

=

v

3

s/3

Hence the mean speed over the distance=

t

1

+t

2

+t

3

s

=

v

1

1

+

v

2

1

+

v

3

1

3

=18km/h

Answer 2

Answer:

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