Directions
Draw a square.
Draw the two diagonals of the square.
Where there intersect is the center of the circle.
Find the midpoint of one of the sides. Draw a line from the midpoint of one of the sides to the center. That's the radius of the circle. Draw the circle.
Now you know what it looks like. How big is the radius?
Solution
Find the length of the side of the square.
The formula for the area of a circle is
Area = s^2 where "s" is the length of the side.
900 = s^2
Take the square root of both sides.
sqrt(900) = sqrt(s^2)
s = 30
The diameter of the circle is the same as s. You can "prove" this by drawing a line from the midpoint of the side of the circle to the center and then to the other side opposite. The side and what you drew are equal.
So the radius of the circle = s/2 = 30/2 = 15
Area of the circle = pi*r^2
Area of the circle = pi * 15^2
Area of the circle = 225 * pi <<< Answer