r=0.9

The area of a circle is equal to Pi π times the radius r squared.

π⋅(radius)2

Substitute in the value of the radius r=0.9 into the formula for the area of a circle. Pi π is approximately equal to 3.14.

π⋅0.92

Raise 0.9 to the power of 2.

π⋅0.81

Multiply π by 0.81.

2.54469004

Find the Area circle (0.9)