How do you find the area of a semi circle with a radius of 7cm?

You should remember that a semi circle is the same as half a circle, therefore the area must be half as well! The formula for the area of a circle is pi r^2. If we use this, the area of our circle = pi x (7^2) = 49 pi. The area of the semi circle is therefore 24.5 pi cm^2.