Follow these steps to identify a direct variation between two variables x and y:
Obtain multiple measurements of the variables, x1, y1, x2, y2, x3, y3,..., xn, yn.
If the ratio of these variables is equal, y1/x1 = y2/x2 = y3/x3 = ... = yn/xn, the variables are directly varying.
Alternatively, plot the readings as points on a graph, (x1, y1), (x2, y2), (x3, y3),..., (xn, yn). If they form a straight line, the variables are directly varying.
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