Answer:
d. m = 15c
Step-by-step explanation:
Directly proportional means as one amount increases, another amount increases at the same rate.
Proportionality can be used to set up an equation.
Given variables:
- m = amount of money earned (in dollars)
- c = number of cars washed
If m is directly proportional to c then: [tex]m \propto c[/tex]
Convert this to an equation by using a constant of proportionality, k:
[tex]\implies m=kc[/tex]
We are told that Paul washed 8 cars and earned $120.
Substitute these values into the found equation and solve for k:
[tex]\implies 120=8k[/tex]
[tex]\implies k=\dfrac{120}{8}[/tex]
[tex]\implies k=15[/tex]
Finally, substitute the found constant of proportionality (k) into the equation:
[tex]\implies m=15c[/tex]
