Question

A car covers a distance of 16km in 15 minutes. Find its speed in km/hr.

Answer 1

Hint: As it asked in the question to report the answer in km/hr, we will convert time which is given in minutes to hours using the relation that 1 hour is equal to 60 minutes. Once you have converted the time in hours, use the formula $ \text{speed=}\dfrac{\text{distance covered}}{\text{time taken}} $ to get the answer to the above question.

Complete step-by-step answer:
Let’s start with what is speed. Speed is a scalar quantity defined as the distance travelled by a particle or object per unit time.
Generally, we deal with two kinds of speeds. One is instantaneous, and the other is the average speed. For uniform motion, both are identical.
Average speed is defined as the total distance covered by a body divided by the time taken by the body to cover it.
 $ \therefore {{v}_{avg}}=\dfrac{\text{distance covered}}{\text{time taken}} $
Now, starting with the solution to the above question. It is given in the question that a car covers a distance of 16km in 15 minutes and we are asked its speed in km/hr. So, the first thing we will do is convert 15 minutes into hours.
We know, $ 1\text{ hour}=\text{60 minutes} $ , so we can say that $ \dfrac{1}{60}\text{ hour}=1\text{ minutes} $ . Using this we can say that $ \dfrac{1}{60}\times \text{15 hour}=1\times 15\text{ minutes} $ , which gives us that 15 minutes is equal to $ \dfrac{1}{4}hrs $ .
Now we will use the formula $ \text{speed=}\dfrac{\text{distance covered}}{\text{time taken}} $ to find the answer to the above question.
 $ \text{speed=}\dfrac{\text{distance covered}}{\text{time taken}}=\dfrac{16}{\dfrac{1}{4}}=16\times 4=64km/hr $
Therefore, we can conclude that the answer to the above question is 64 km/hr.

Note: Don’t forget to convert the elements given in the question to the units which you are asked to report the answer before using them in calculation as we did for 15 minutes in the above question. Also, be careful that you don’t forget the formula $ \text{speed=}\dfrac{\text{distance covered}}{\text{time taken}} $ or confuse it with $ \text{speed=distance}\times \text{time} $ , which is a common mistake made in a hurry.