Question

the car travels 15 minutes by second and then another 18 minutes in 6 seconds what is average speed of a car​

Answer 1

The easiest way is to multiply 15 km by 3 because 20 minutes is a fraction of 1/3 from an hour which give an answer of 45km/h.

The fundamental way to solve this type of question is to do unit conversion. The velocity (or speed) of the car is  15km/20minutes . Since the unit of time is in minute instead of hour, we need to change it.

In order to change it, we need to multiply  15km/20minutes  by  60minutes/1hour  so the result is  45km/1hour  which normally pronounced as km per hour.

I’ll do another example for you but this time, the initial velocity is given in meter per second. Let say a bike is travelling at 2 meter per second and we are looking for its velocity in km/h.

First, you need to know the conversion ratio which is 1 km = 1000 meter (kilo means 10^3) and 1 hour is 3600 seconds (60 seconds*60 minutes = 3600 seconds).

Now, write down the initial speed with unit which is  2meter/1second  and multiply it with the conversion ratio. In this case,  2meter/1second  times  1km/1000meter  times  3600second/1hour  and the answer will be 7.2 km/h . This looks hard in linear form but it will look easier in stacked form because it is easier to see the unit cancel out each other.