If A and B are each circles, what is the radius of the larger circle?
Larger Circle radius = R ; Smaller Circle radius = r

1) Larger circle's circumference is 4 times the circumference of the smaller circle.

\(2πR=4(2πr)\)
\(R=4r\)
To find the area we need exact value of r. As R=4 and r can be 1 or R=400 and r =100 we can get different areas for the proportional radii. So not sufficient

2) The area of A minus the area of B is \(20π\)
\(πR^2-πr^2=20π\)
\(R^2-r^2=20\)

From 1 and 2
Equate R=4r into \(R^2-r^2=20\)
Since this is a DS question you can stop here you would be able to find the exact values of r and R so answer is C.

But if its a PS question
\(4r^2-r^2=20\).......=>(4r)^2-r^2=20
\(r^2=4/3\)
\(r=2/√3\)
Then
\(R=8/√3\)
\(πR^2=π8/√3)^2\)

I do however have a doubt
Am i wrong in thinking that Area A can be the bigger circle and area b is the smaller circle. No where in the question is the relation between large small a and b given. So if this question did come up in the test. Could the answer be E????