Question 288727
Recall that the equation of a line is y=mx+b, where m is the slope and b is the y-intercept.


'Varies directly' just means that the slope is constant, and the y-intercept is zero.


The variation constant is just another word for the slope.


C=kr
94.2=k*15
k=6.28

Your equation is:


C=6.28r