A relationship between two variables in which the dependent variable is the sum of a constant number and a constant multiple of the independent variable.

Partial variation can be written in the form y = kx + c, where x and y are variables and k and c are some real constants. y = mx + c (where m and c are constants) is an equation of straight line which can be an example of partial variation because, we can see that y varies partially according to the value of x.

Definition

If there is a relationship between two variables where the dependent variable is the sum of a constant multiple of the independent variable and a constant number, then the relationship is called partial variation. In other words, a quantity y is partly constant and partly varies directly as x, then the law of variation can be expressed as

y α a + x,
That is,
y = a + kx,
where a and k are constants.