This is quite easy as it is simply knowing the formulas to solve different portions of the circle.
(A) To solve for circumference, the formula is d*pi where d is the diameter. The diameter is simply twice the radius, so we can just double 11 for it. This means 22 is the answer.
(B) The formula for area of a circle is pi*r^2, so for this one, we just need to square the radius. 11 squared is 121.
(C) To solve this, we should solve for the area of the circle, and then multiply it by 3 to represent the 3 dollars. To solve the area, we just substitute 11 into the formula for r. Afterwards, we should multiply it by 3 for the reason above. However, because we used 3.14 instead of pi, we must say the cost is approximately $1139.82. <span />
