Question

The sum of the area of 2 circles is 80pi square meters. Find the length of a radius of each circle if one of them is twice as long as the other.

smaller circle- r
larger circle- 2r
what is the radius of the larger circle?

Answer 1

8 is the correct answer

Answer 2

80p=pr^2+p(2r)^2
80p=pr^2+4pr^2
80=r^2+4r^2
80=5r^2
16=r^2
r=4 for the smaller circle´s radius, and 8 is the larger circle´s radius.

Have a nice day, I hope this was helpful :D