Use Direct and Inverse Variation: example 8.90

If y varies inversely with $x$ and $y = 20$ when $x = 8$ , find the equation that relates x and y.

Work it out on paper first. Then open the solution one step at a time, and stop as soon as you can finish on your own.

Your turn

The book's Try It right after this example: same idea, new numbers. Only the answer is given.

If $p$ varies inversely with $q$ and $p = 30$ when $q = 12$ find the equation that relates $p$ and $q .$

How did it go?

Write the formula for inverse variation.
Substitute the given values for the variables.

Solve for the constant of variation.

Write the equation that relates $x$ and $y$ .
Substitute in the constant of variation.

Write the formula for inverse variation.
Substitute the given values for the variables.

Solve for the constant of variation.

Write the equation that relates $x$ and $y$ .
Substitute in the constant of variation.