Question

if the radius of a circle is increased by 4 inches, the area of the resulting circle is 100pi in^2. Fin the radius of the original cricle,

Answer 1

A = pi * r^2

We can let

r = x + 4

since the radius has been increased by 4. Where does the 100 pi go?

Answer 2

x?

Answer 3

Hmmmm ..... how about area?

Answer 4

ah ok

Answer 5

100 pi = pi * (x+4)^2

then divide both sides by pi

100 = (x+4)^2

All is good?