Sam Z. answered • 08/11/19

Math/Science Tutor

To get the area of a cylinder you need the circumference which is dpi.

In your case 200pi is the area.

(200pi-(r^2pi*2))/21=the circumference=dpi

(628.32-(6.28*r^2))/21

628.32/21=29.92

6.28/21=.3

29.92-(.3r^2)=dpi

29.92/pi-(.3/pi*r^2)

9.52-.095r^2=d

4.76-.0475r^2=r

Shane H.

I still don't see how you got 4?08/07/19