The area of a circle varies directly with the square of the radius. Since A = πr2, the constant of variation is π. Which of the following examples illustrates direct variation. Identify the constant of variation. A. The circumference of a circle varies directly with the radius. The constant of variation is 2π.
B. The average of 2 numbers varies directly with either number. The constant of variation is the other number.
C. The slope of a line varies directly with the y-intercept. The constant of variation is the slope.
D. The distance between a number and 0 varies directly with the number. The constant of variation is the number.