circumference=2*pi*r or pi*d so if its 16pi you know that your diameter is 16 wich means your radius is 8 because d/2 is your radius. plug the 8 into the area formula wich gives you the formula pi*8^2. 8squared is 64. 64 times pi is 201. or 64pi wich is the area of the same circle with the circumfernce of 16pi
