write an equation that models the situation

[fallinbehind]

use k to represent the variation constant

the amount of material needed to cover a ball varies directly with the square of the radius. it takes about 172 cm^2 to cover a ball with a radius of 3.7 cm. What is the radius of a ball that needs 366cm^2 of material to cover it?

 

[ting]

Let the amount of material be, m, and the radius, r.


Then

m is proportional to r^2


m = kr^2


Substitue in known values and solve for k.

172 = k*3.7^2

k = 12.56(...)

Then use

m = 12.56r^2


Substitute in 366 and solve for r. (Don't forget to find the sqrt.)