Question

how many minutes does aditya take to cover a distance of 400 m if he runs at a speed of 20 km/hr

Answer 1

400 mts with 20kmph
4000 mts=0.400km
NOW
time=distance/speed
time=0.400/20
Time=0.02 hours
IN minutes=0.02*60
1minute 20 seconds

Answer 2

1.2012 minutes is taken by Aditya to cover 400 m distance if the speed is 20 km/hr

Solution:

To find the time required by Aditya to cover 400 m, if his speed in 20 km/hr.

Now to find the time required to cover a certain distance over a certain speed,

$\bold{Time =\frac{\text {Distance}}{\text {Speed}}}$

Now in most of the cases the units of divisor and dividend should be same but here we can see that the speed is in km whereas the distance is in meter.

Now let us first familiarize the units of both the distance and speed  

To convert speed into mph from km/hr we multiply 20 by $\frac{5}{18}$ ; we get 5.55 mps

$20 \times \frac{5}{18}=5.55$

Speed = 5.55 km/hr

Now, let us find the value of time, we get

$\frac{400}{5.55}=72.072\ seconds$

Time taken in minutes is $\bold{\frac{72.072}{60}=1.2012\ minutes}$.