Find the circumference and area of a circle with a diameter of 6 cm using pi

Formula of circumference is
C=π*d, where d is a diameter.

So, 
C=6π (cm) is exact value,
C≈18.85 (cm) is an approximate value.

Since we know the diameter is 6, then its radius has to be half that, or 3.

Circumference of a circle
C = 2πr,   r = 3
C = 2π3 => C = 6π

Area of a circle
A = πr²
A = π3² => A = 9π