1. FIRST QUESTION.
M is directly proportional to

Suppose you have two variables, say,
. We say that
varies directly as
or, in other words,
is directly proportional to
if and only if:
Where
is a nonzero constant called the constant of proportionality.
Knowing this, we can solve this problem. Here
is directly proportional to
. So:

We know that when
, hence the constant of proportionality can be found as follows:

So:

PART A)
When
, then:

PART B)
When
, then:
![540=(5)/(2)(r^3) \\ \\ r^3=(2(540))/(5) \\ \\ r^3=216 \\ \\ r=\sqrt[3]{216} \\ \\ \boxed{r=6}](https://img.qammunity.org/2020/formulas/mathematics/middle-school/wodhawyxg58okpdzlzced2lkvz8iw3wrtz.png)
2. SECOND QUESTION.
M is directly proportional to

We know that when
, hence the constant of proportionality is:

So:

PART A)
When
, then:

PART B)
When
, then:
