I believe that your basic question is the difference between a variable and a parameter.

Many math instructors are rather loose with the vocabulary; in particular they will define a variable as a letter/symbol taking the place of a number. But there is a difference between a physical constant, a constant, a parameter, and a variable.

A physical/mathematical constant is a number that arises in particular applications so often that we represent it with a letter/symbol. Thus `pi,phi` in math, or c for the speed of light, etc... are constants.

Other constants aren't as prevalent or have a specific utilization. Specific substances have a specific boiling point, measure of elasticity, albedo, etc...

A variable is allowed to change within the application/procedure/algorithm. Thus we are allowed to change "x" in an algebraic equation and "y" will then possible change.

A parameter does not change in a specific application, but takes on different values from application to application. Pythagoras's theorem `a^2+b^2=c^2` applies to all right triangles, but are unchanged if you are give a specific triangle.

A good example of parameters at work is the equation for a parabola. `y=ax^2+bx+c` ; for a specific parabola a,b, and c remain unchanged while x and y are allowed to change.

I believe that your basic question is the difference between a variable and a parameter.

Many math instructors are rather loose with the vocabulary; in particular they will define a variable as a letter/symbol taking the place of a number. But there is a difference between a physical constant, a constant, a parameter, and a variable.

A physical/mathematical constant is a number that arises in particular applications so often that we represent it with a letter/symbol. Thus in math, or c for the speed of light, etc... are constants.

Other constants aren't as prevalent or have a specific utilization. Specific substances have a specific boiling point, measure of elasticity, albedo, etc...

A variable is allowed to change within the application/procedure/algorithm. Thus we are allowed to change "x" in an algebraic equation and "y" will then possible change.

A parameter does not change in a specific application, but takes on different values from application to application. Pythagoras's theorem applies to all right triangles, but are unchanged if you are give a specific triangle.

A good example of parameters at work is the equation for a parabola. ; for a specific parabola a,b, and c remain unchanged while x and y are allowed to change.

SORRY but my question is that why we use parameter

example

length of rectangle filed is 150m and its width is 125m.find the cost of fencing it at the cost rs 15 per square meter

ans.

l=150m

w=125m

parmeter =2(150+125)

=550

cost of fencing @10% parameter is 550×10= 5500

area=150×125=18750

cost of fencing @15% parameter=18750×15=281250

my question is that why we use parameter in this solution.