Question

The sum of the areas of two circles is 80 pi

Answer 1

The area of a circle is A = πr^2. We let A1 And A2 the areas of the circles and r1 and r2 the radius of each, respectivley.

A1 + A2 = 80π
Substitute the formula for the area,
π(r1)^2 + π (r2)^2 = 80π

From the statement, we know that r2=2(r1).

π(r1)^2 + π (2 x r1)^2 = 80π
We can cancel π, we will have

5 x (r1)^2 = 80
Thus,

r1 = 4 and r2 = 8