SOLUTION: the radius of a circle is 3m. what is the circumference of another circle, whose area is 40times that of the first?

Algebra ->  Rectangles -> SOLUTION: the radius of a circle is 3m. what is the circumference of another circle, whose area is 40times that of the first?       Log On


   

Question 365946: the radius of a circle is 3m. what is the circumference of another circle, whose area is 40times that of the first?
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
Let r = radius of the bigger circle. Then %28pi%2Ar%5E2%29%2F%289pi%29+=+40.
r%5E2%2F9+=+40, or r%5E2+=+360. Hence r+=6%2Asqrt%2810%29. Thus the circumference of the bigger circle is C+=+2pi%2Ar+=+2%2Api%2A6sqrt%2810%29+=+12%2Api%2Asqrt%2810%29 meters.