Question

8. A man walks 6 km at 12 km/h and returns at 10 km/h. Find his average speed.​

Answer 1

Given:

A man walks a distance of 6 km at a speed of 12 km/h

The man returns at a speed of 10km/h, so he will return to the same distance 6 km

Now,

We know that,

$\boxed{\bf Speed = \frac{Distance}{Time}}$

We can get,

$\bf Time = \frac{Distance}{Speed}$

So,

The time taken by the man to travel 6 km at speed of 12 km/h is

$\sf Time (t_{1}) = \frac{6}{12} = \frac{1}{2} = 0.5\ hour$

Now,

When he returns, distance = 6 km and speed is 10 km/h

$\tt Time(t_{2}) = \frac{6}{10} = 0.6 hour$

Now,

$\bf Average\ Speed = \frac{Total\ distance}{Total\ time}$

$\bf Average\ Speed = \frac{6 +6}{0.5+0.6}$

$\bf Average\ Speed = \frac{12}{1.1}$

$\bf Average\ Speed = 10.9\: km/h$

Hence,

• The average speed is 10.9 km/h

Answer 2

Answer:

10.9 km/h

Step-by-step explanation:

Given -

Man walks 6 km at 12 km/h and returns (6km) at 10 km/h

To find -

The average speed

Solution -

Average speed = Total distance/total time

First we have to find Total time because distance already given.

Time taken by the man for first walk 6 km at 12 km/h =

= 6km/12 km/h

= 6/12 h

= 1/2 h

= 0.5 h

Time taken by the man for return walk 6 km at 10 km/h

= 6 km/10 km/h

= 6/10 h

= 3/5 h

= 0.6 h

Now average Speed = Total distance / total time

= (distance first walk + second walk)/ (time taken first+second)

= (6 km+6 km)/(0.5 h + 0.6 h)

= 12 km/1.1 h

= 10.9 km/h (approx)

Hence the average speed of the man = 10.9 km/h.

hope it helps.