Enter any 2 values (the constant of variation, the x-value, or the y-value) into the direct variation calculator. The calculator can calculate the missing X or Y value, or the constant of direct variation, given any 2 of the 3 variables.
Direct Variation Formula
The following formula is used for calculating a direct variation.
C = Y/X
Y = CX
- Where C is the constant of direct variation (also called the constant of proportionality)
- X is the independent variable and Y is the dependent variable.
To calculate a direct variation, find the constant by dividing Y by X (using a known pair of values), then multiply that constant by the X value you want: Y = CX.
The equation y = Cx is a special case of slope-intercept form (y = mx + b) with b = 0, so the line passes through the origin. If b is not zero, the relationship is linear but it is not a direct variation.
Direct Variation Definition
A direct variation is a relationship between two variables where one variable is directly proportional to the other at a constant rate. It is commonly written as y = Cx, where C is a constant.
How to calculate direct variation?
How to calculate direct variation?
- First, determine the constant of direct variation.
This is C in the formula above (y = Cx). This constant is also the slope of the line. For this example, the constant C is 5.
- Next, determine the value of x (or y).
Determine the value of one variable. For this problem, we know x to be 4.
- Finally, calculate the missing variable.
Using the formula above, calculate the missing variable. Y = 5*4 = 20.
Direct vs Indirect Variation
A direct variation, as is outlined above, is a situation in which a variable is directly proportional to some other variable via a constant.
If the constant is positive, then as one variable increases, the other increases (and as one decreases, the other decreases). If the constant is negative, then as one increases, the other decreases.
Indirect variation, or sometimes referred to as inverse variation, is the relationship between two variables in which one is inversely proportional to the other.
This equation would look something like y = C/x (equivalently, xy = C). For a positive constant, as one variable increases, the other decreases, and vice versa.
FAQ
A direct variation is a relationship between two variables where one is proportional to the other. Typically this is described in the form y = cx, where c is the direct variation constant.
Direct variation can be used when two variables have a constant ratio (y/x is constant) and the relationship can be modeled by y = c x. For example, if B increases by 2 for every 1 increase in A (and B is 0 when A is 0), then B = 2A. This means that if A = 4 then B = 8.
