Question

A person crosses an \[600\]m long street in \[5\] minutes. What is his speed in km per hour?

Answer 1

Hint: We can solve this sum by unitary method. The distance covered in one minute gives us the speed of the person in one minute. Then we can convert it into km and hour.

Complete step by step answer:
It is given that a person crosses an \[600\]m long street in \[5\]minutes.
We have to find the speed of the person in kilometers per hour.
We know that, \[1\]hr\[ = 60\]min
Now we will convert the given time minutes into hours so that it would be helpful in finding the speed of the person in kilometre per hour
So, \[5\]min \[ = \dfrac{5}{{60}}\]hour
Also we know that, \[1\]km \[ = 1000\]m
Now we will convert the given distance in meters to kilometre so that it would be helpful in finding the speed of the person in kilometre per hour
So, \[600\]m \[ = \dfrac{{600}}{{1000}}\]km
Now we have,
In \[\dfrac{5}{{60}}\]hour the person crosses \[\dfrac{{600}}{{1000}}\]km,
To find the speed of the person who crosses the street we will divide the distance he covered by the time taken,
So in \[1\] hour, the person crosses \[\dfrac{{\dfrac{{600}}{{1000}}}}{{\dfrac{5}{{60}}}}\]km/hour.
On simplifying the above equation we get,
The speed of the person is \[\dfrac{{600}}{{1000}} \times \dfrac{{60}}{5}\]km/hour
By cancelling the terms in the above equation, we get, \[7.2\]km/hour.

Hence, we have calculated the speed of the person as\[7.2\]km/hour.

Note:
Alternative way of solution:
We also know that, Distance = Speed \[ \times \] time
With the help of the formula we can substitute the time and distance in the given problem and calculate the speed.
Substitute distance \[ = \dfrac{{600}}{{1000}}\]km and time \[ = \dfrac{5}{{60}}\]hour we get,
Speed \[ = \dfrac{{\dfrac{{600}}{{1000}}}}{{\dfrac{5}{{60}}}}\]km/hour
Simplifying we get, the speed is \[7.2\]km/hour.