Question

Ruchi cycles from metro station A to another metro station B at 18 km/hr and returns back to the metro station A at 12 km/hr. Find her average speed during the entire journey?

Answer 1

Given: Speed from A to B$=18km/h$

Speed from B to A$12km/h$

To find: Ruchi's average speed.

Solution:

Let distance from A to B be x km.

Understand that, time taken to travel from A to B$\[ = \frac{x}{{18}}hr\]$

time taken to travel from B to A$\[ = \frac{x}{{12}}hr\]$

Find the average speed during the entire journey.

$\[Average\,speed = \frac{{Total\,dis\tan ce}}{{Total\,time}}\]$

                       $\[ = \frac{{2x}}{{\left( {\frac{x}{{18}} + \frac{x}{{12}}} \right)}}\]$

                       $\[ = \frac{{2x}}{{\left( {\frac{{2x + 3x}}{{36}}} \right)}}\]$

                       $\[ = \frac{{2x}}{{\frac{{5x}}{{36}}}}\]$

                       $\[ = \frac{{2 \times 36}}{5}\]$

                       $\[ = \frac{{72}}{5}\]$

                       $\[ = 14.4km/h\]$

Hence, the average speed during the entire journey is $\[14.4km/h\].$

                       

Answer 2

Answer:

14 km

Step-by-step explanation:

Ruchi cycles from metro station A to another metro station B at 18 km/hr and returns back to the metro station A at 12 km/hr. Find her average speed during the entire journey?