FACT or BLUFF

Direct Variation

The value of y varies directly with the value of x if there exists a nonzero constant k.

Inverse Variation

The value of y varies inversely with the value of y if there exists a nonzero constant k.

Joint Variation

The value of y varies jointly with the value of x and z if there exists a nonzero constant k.

Constant of Variation

It is the nonzero number k that does not change the value.

Combined Variation

The value of y varies directly as x and jointly as z.

On planet X, an object falls 32 feet in 2 seconds. Knowing that the distance the object will fall varies directly with the square of the time it falls, how long does it take an object to fall 200 feet?

The amount of weight on a spring and the distance the spring will stretch is an example of Inverse Variation.

The cost of a taxi fare (c) varies directly as the distance (d).

The number of hours you work and the amount of paycheck is an example of Direct Variation.

The Intensity I of light received from a source varies inversely as the square of the distance d from the source. If the light intensity is 4 feet candles at 11 feet, find the light intensity at 13 feet.