Which formula is used To find the area of a circle When given the radius

The options are
a=d.d
a=r.r
a=2.2
a=r

3 answers

The correct formula to find the area of a circle when given the radius is:

a = π * r^2
Choose one of the options pls
The correct formula to find the area of a circle when given the radius is:

a = r * r