Answer: Area of circle = 12.57cm² (I am assuming you mean area here)
Explanation:
Area = πr²
radius = diameter ÷ 2
r = 4 ÷ 2
r = 2
π = 3.14159265359
shorten π to 3.14 for future reference. I just used the π button a a calculator for this answer though.
A = π × 2
A = 12.57