What is proportional relationship in math terms?

Answer 1

Two variables are proportional to one another if there is a simple relationship, of the following form:

The variables X and Y are in

direct proportion if Y = c*X

and

inverse proportion if Y = d/X or, equivalently, X*Y = d

for some non-zero constants c and d, called the constants of proportionality.

Note that if Y is inversely proportional to X, then Y is directly proportional to the variable 1/X

The graph of a direct proportion is a straight line through the origin, with slope = constant of proportionality.