An outside circular ring has a circumference of 200 cm. What is the circumference of an inner ring which is 25 cm shorter in radius? Both circles have the same center.

First, find the circumference of the outer ring. The formula to be used is

C = 2*pi*r

200 = 2*pi*r

r = 31.83 cm

Since, both rings are concentric, just subtract 25 from the radius of the outside ring to find the radius of the inner ring

radius of inner ring = 31.83 - 25

radius of inner ring = 6.83

Then, we use this radius to the formula to find its circumference:

C = 2*pi*6.83

C = 42.91 cm

Find circumferences

c=2pir

200=2pir

divide by 2

100=pir

divide by pi

100/pi=r

aprox

31.83099=r

25 les than that is

6.83099

c=2pir

c=2*3.141592*6.83099

c=42.9204

about 43cm