Two circular disks

The length of the cord will be the sum of: (check the dig below)
1. length of the two red lines
2. length of the two green lines
3. difference between the circumference of the circles and the purple portion of the circumference.

1. length of the two red lines = 80 + 80 = 160 (since the radius of the bigger circle and the red lines make a square)
2. length of the two green lines = 60+60 = 120

3. Purple portion of the circle A = ¼ 2 pi R = ½ pi 80 = 40 pi
Purple portion of the circle B = 30 pi
Circumference of circle A = 2 pi R = 160pi
Circumference of circle B = 2 pi r = 120 pi
Difference = (160pi – 40pi) – (120pi – 30pi) = 210pi

Hence the length of the cord is 210 pi + 160 + 120 = 210pi + 280

Answer is B

mals24 wrote: Difference = (160pi – 40pi) – (120pi – 30pi) = 210pi

(160pi – 40pi) + (120pi – 30pi)

just take the length of the rope touching the circles to be 3/4 of circumference.

@ alescau

Hey sorry dint think of it that way thanks for the idea