1. Area of a circle with radius r is given by the formula: A= pi x r^2

2. Area of a circle using an approximation of pie is = 3.1416 x r^2

3. I used pie = 3.1416 for approximation in (2) because it provides area directly in decimal form and easy to calculate with a calculator. Another approximation of pi is 22/7which does not provide answer directly in a decimal number.