At reasons in between greatnesses different are the division between the measurements of greatnesses different. If the reason is represented in the form of fraction and the numerator is a measure of time, for example, the denominator must be a measure of another greatness different from time.
To better understand this division, it is important to remember that greatness it is everything that can be measured, that is, everything that has some characteristic that can be represented numerically.
Reasons in between greatnessesdifferent they can have a very important meaning for the modern man and bring information of great use to him. Below, see some of these reasons, examples of their calculations and their usefulness.
Average speed
Average speed (V) is the result of reason between the distance covered (S) and the time spent on the route (t). In Brazil, these greatnesses are expressed in kilometers and hours, respectively. In this way, calculate the velocityaverage of an object is to find out how many kilometers can be covered in an hour. Generally, this reason is expressed as follows:
V = s
t
The unit of measure of velocity is km/h (kilometers per hour).
As an example, imagine a car that traveled a distance of 800 km and took 8 hours to do so. The average speed of this car on this route was:
V = s
t
V = 800
8
V = 100 km/h
Now imagine that a person wants to travel from his city to his parents' city, 400 miles away, for an appointment at 6:00 pm. Knowing that you can only travel to one velocityaverage of 80 km/h, at what time should this person leave the house, at the most, to fulfill his/her commitment?
Again, use reason velocityaverage:
V = s
t
80 = 640
t
Note that this time we need to know the time, and not the velocity. Therefore, the substitution in the formula was done that way. Continuing:
80t = 640
t = 640
80
t = 8 hours
So, it is necessary to leave within a maximum of 10 hours to arrive at 6 pm at the intended destination.
Average consumption
Average consumption (C) is the reason between the space traveled (S) and the volume of fuel used (v). The units of measure of these greatnesses are kilometers and liters, respectively. When we calculate this ratio, we are interested in finding out how many kilometers it is possible to run on 1 liter of fuel. That reason is usually expressed as follows:
C = s
v
The unit of measure of the consumptionaverage is km/l (kilometers per liter).
A car that can run 280 kilometers on 20 liters of fuel has what average consumption?
C = s
v
C = 280
20
C = 14 km/l
This car can travel 14 km on just one liter of fuel. Note that it is possible to predict the amount of fuel that will be spent on trips based on the vehicle's average consumption. A car that develops 14 kilometers for every liter of fuel, for example, will consume how many liters of fuel in a 2800 km journey?
C = s
v
14 = 2800
v
14v = 2800
v = 2800
14
v = 200 liters.
Demographic density
And the reason between the number of inhabitants (inhabitant) of a given region and the area total (A) of that region. The units of measure of these greatnesses are, respectively, inhabitants and kilometers square. This reason is usually expressed as follows:
D = hab
THE
This ratio is used to calculate the number of inhabitants of a given region per square meter.It is very important because it points out in a way proportional the number of inhabitants of the cities.
The Brazilian demographic density, for example, is 24.3 inhab/km2. The demographic density of the state of São Paulo is approximately 180 inhabitants/km2. This means that most of the Brazilian population resides in this state.
By Luiz Paulo Moreira
Graduated in Mathematics
