The formula for the area, A, of a circle in terms of its radius, r, is given by:
A = πr2
To work out the shaded area shown below, we must work out the area of the outer circle and subtract the area of the inner circle.
Calculate the shaded area in cm2 between the two circles shown below.
Give your answer to 3 sig. figs.
Area of outer circle = π x 92 = 81π
Area of inner circle = π x 82 = 64π
Shaded area = 81π - 64π = 17π = 53.4 cm2 (3 s.f.)