Area and circumference of a circle

How to use it

1. 1Halve a given diameter before substituting: the formulas take the radius, and the diameter is what questions usually print.
2. 2Take $\pi =\frac{22}{7}$ whenever a radius or diameter is a multiple of $7$, and leave $\pi$ symbolic when the options do.
3. 3Eliminating $r$ between the two formulas gives $A=\frac{C^2}{4\pi }$, which is what comparisons at a fixed perimeter need.

Step-by-step

1. 1
   $2\times \frac{22}{7}\times r=88\Rightarrow r=14$ m

   Why: Solve the circumference formula for the radius first.

2. 2
   $A=\frac{22}{7}\times 14^2=616$ m${}^2$