Question

A dog is walking at a speed of 6km/hr. How much time would it take to cover 200 metres?

Answer 1

Hint: Given that a dog is walking at a speed of 6km/hr. Speed is calculated as distance/time which gives distance=speed × time and time is distance/speed. Speed is given in kilometres per hour, convert it into meters per second. Using the speed and distance given, find the time it would take by the dog to cover 200 metres.

Complete step-by-step answer:
We are given that a dog is walking at a speed of 6 kilometres per hour.
We have to calculate the time it would take to cover 200 metres.
 $
  speed = \dfrac{{dist}}{{time}} \\
  time = \dfrac{{dist}}{{speed}} \\
  $
The dog can walk 6 kilometres per hour. Convert the speed in terms of metres per second.
1 kilometre is equal to 1000 metres and 1 hour is equal to 3600 seconds.
 $ 6\dfrac{{km}}{{hr}} = 6 \times \dfrac{{1000m}}{{3600\sec }} = 6 \times \dfrac{{5m}}{{18\sec }} = \dfrac{{15}}{9}m/\sec $
The dog can walk 15/9 metres per second.
We have to calculate the time for 200 metres.
 $
  time = \dfrac{{dist}}{{speed}} \\
  speed = \dfrac{{15}}{9}m/\sec ,dist = 200m \\
   \Rightarrow time = \dfrac{{200}}{{\left( {\dfrac{{15}}{9}} \right)}} \\
   \Rightarrow time = \dfrac{{200 \times 9}}{{15}} \\
  \therefore time = 120\sec \\
  $
Therefore, the dog takes 120 seconds which can also be said as 2 minutes, as 1 minute is equal to 60 seconds, to cover a distance of 200 metres with a speed of 6 kilometres per hour.

Note: When a speed is given in Kilometres per hour, to convert it into metres per second just multiply $ \dfrac{5}{{18}} $ to the given speed value. And when the speed is given in metres per second, to convert it into kilometres per hour multiply $ \dfrac{{18}}{5} $ to the given speed value. So do not confuse kilometres with metres and vice-versa.