Which of the following equations describes a relationship of inverse variation between input and output?
a.) output=constant/input
b.) output=constant–input
c.) output=constant •input
d.) output=input/constant

The correct answer is:

A) Output = Constant/Input.

Explanation:

Inverse proportion is also called inverse variation. In inverse variation, as one variable increases, the other decreases, but their product stays the same. 

Algebraically their product would be represented by the equation
xy=k.

To isolate the output, y, we would divide both sides by x:
xy/x = k/x
y=k/x

In this equation, y is the output, x is the input, and k is called the constant of proportionality.

 Based on this, the correct choice is output = constant/input.

It would take her 20 minutes.