Question

A car travels 1/3 of the distance on a straight road with a velocity of 10km/hr, next one-third with velocity 20km/hr and the last one-third with velocity 60km/hr. What is the average velocity of the car in the whole journey? (FULL METHOD)

Answer 1

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Answer 2

Answer:  The average velocity of the car in whole journey is 18 km/hr.

Explanation:

Given that,

Velocity $v_{1} = 10\ km/hr$

Velocity $v_{2} =20\ km/hr$

Velocity $v_{3} = 60\ km/hr$

Let us considered the total distance is 3x and total time is T.

Using formula,

Velocity = distance/time

The time for first journey

$t_{1}= \dfrac{3x}{3\times10}$

$t_{1}= \dfrac{x}{10}$

The time for second journey

$t_{2}= \dfrac{3x}{3\times20}$

$t_{2}= \dfrac{x}{20}$

The time for third journey

$t_{3}= \dfrac{3x}{3\times60}$

$t_{3}= \dfrac{x}{60}$

Average  velocity = total distance / total time

$v = \dfrac{D}{T}$

Put the value of total distance and total time

$v = \dfrac{3x}{\dfrac{x}{10}+\dfrac{x}{20}+\dfrac{x}{60}}$

$v = \dfrac{3x\times60}{10x}$

$v = 18\ km/hr$

Hence, The average velocity of the car in whole journey is 18 km/h.