Your answer is 8.626 Because it's a square, you know that each side is 8 because √64 = 8. This also tells you that the radius of each of the outer circles is 4. Because each side of the square is 8, you can use Pythagoras' Theorem to find the diagonal, and do 8² + 8² = 64 + 64 = 128, so √128 is the diagonal (I'm leaving it in surd form because it's a pretty long number). You first need to divide √128 by 2, because you're trying to find the radius of circle O, so that gives you 5.657. Because you know that the radius of the outer circle is 4, you can subtract 4 from this and get 1.657 as your radius. Now, we can use this to find the area of the circle by doing π × 1.657² = 8.626.
