Question

A car travels x km at 60 km/hour

Answer 1

Explanation:

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Given:

A car travels x km at 60km per hr and then travels another 2x km at 40km/hr.

To find:

The average speed for the entire distance.

Solution:

As we know that when an object is moving at a speed 's' and covers distance 'd' in time 't' then its speed is given by:

$s = \frac{d}{t}$

So,

As given,

The speed of the car when it travels x km = 60 Km/hr.

So, the time that is taken by the car to travel x km

$= \frac{x}{60} hr$

Also,

the speed of the car when it travels 2x km = 40 Km/hr.

So, the time that is taken by the car to travel 2x km.

$= \frac{20}{40} km$

$= \frac{x}{20} km$

Hence,

the average speed for the entire distance.

$= \frac{total \: distance \: travelled}{total \: time \: taken}$

$= \frac{x + 20}{ \frac{x}{60} + \frac{x}{20} }$

On solving the above, we get

$= \frac{3}{ \frac{x + 3x}{60} }$

$= \frac{3x}{ \frac{4x}{60} }$

$= \frac{3 \times 60}{4}$

$= 3 \times 15$

$= 45 km / hr$

Hence, the average speed for the entire distance is 45 km/hr.

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