Choose the One Alternative That Best Completes the Statement or Answers

Multiple Choice

Choose the one alternative that best completes the statement or answers the question.
Write a variation model using k as the constant of variation.
-The variable m is directly proportional to n.

A) $m = \frac { k } { n }$
B) $m = k n$
C) $m = k + n$
D) $n = \frac { k } { m }$