The term "direct variation" refers to a mathematical correlation between two variables where one variable can be represented as a constant multiple of the other unknown quantity. It is also known as a "direct proportion."
The general formula for a direct variation is given as y = kx, where "y" and "x" indicate the variables and "k" denotes a constant number. This formula can be interpreted as "y varies directly with x" or "y increases or decreases by the same factor as x." An example of a standard mathematical formula that is directly proportional is A = pi * r2, where the area of a circle, denoted by "A," varies proportionally with the square of the radius, indicated by "r," by the constant of variation "pi," which is roughly equivalent to 3.1416.