Question

A car is moving on a straight road covers one third of the distance with a speed of 20 km/h and the res
a speed of 60 km/h. The average speed of the car is
(1) 40 km/h
(2) 50 km/h
(3) 36 km/h
(4) 55 km/h​

Answer 1

Answer:

Given:

⅓rd distance travelled by 20 km/hr and the rest distance travelled by 60 km/hr

To find:

Average speed of the body

Concept:

Average speed is defined as the ratio of Total distance to the total time taken.

Since distance is involved , average speed can never be zero, it's always positive.

Calculation:

Let the total distance travelled be s , Then distance travelled with 20 km/hr is s/3 , the rest 2s/3 is travelled with

60 km/hr.

$v \: avg. = \dfrac{total \: distance}{total \: time}$

$= > v \: avg. = \dfrac{s}{( \dfrac{ \frac{s}{3} }{20}) + (\dfrac{ \frac{2s}{3} }{60}) }$

$= > v \: avg. = \dfrac{1}{ \dfrac{1}{60} + \dfrac{1}{90} }$

$= > v \: avg. = \dfrac{1}{ \dfrac{(3 + 2)}{180} }$

$= > v \: avg. = \dfrac{180}{5}$

$= > v \: avg. = 36 \: km \: {hr}^{ - 1}$

So final answer :

$\boxed{ \red{ \large{ \sf{ \bold{ v \: avg. = 36 \: km \: {hr}^{ - 1}}}}}}$

Answer 2

Answer:

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