She got the formula for the area of a circle wrong - it's 𝝅 x radius squared, not 𝝅 x radius x 2. You can see why she slipped up, though.

The radius of the large circle is 10 cm, while the diameter of the smaller circle and semicircles are 10 cm, which divided by 2 gives us a radius of 5 cm.
The correct formula is 𝝅r^2 (Pi times radius to the power of 2), so the larger circle is 𝝅10^2 = 314.15 cm squared.
The head is 𝝅5^2 = 78.52 cm squared. The semi circles have identical radius and diameter, and since there's two adding both their areas gives a full circle so the previous formula gives us the same answer of 78.52 cm squared.
So in conclusion: Body 𝝅10^2 = 314.15 cm squared. Head 𝝅5^2 = 78.52 cm squared. Feet 𝝅5^2 = 78.52 cm squared

A Nun should always know how Duck-Algebra works.