Step One
Develop a formula for the perimeter.
Argument
What you see is a semicircle going upwards and another one going downwards. Two semicircles =1 circle.
The "perimeter" [Circumfrence] of a whole circle = 2*pi*r
We are told that whatever you call this the perimeter is 8pi + 16
Step Two
Set up the equation
8pi + 16 = 2*pi*r + 4r Including the line connecting these two.
Step Three
Take out the common factors on the left and right.
8(pi + 2) = 2r(pi + 2) Divide both sides by pi + 2
8 = 2r Divide by 2
4 = r
Sorry. I didn't know the meaning of perimeter. Mathmate is perfectly correct.
