The formula for area of a circle is A=pi*r^2, but because we know that a semi circle is half of a circle we would divide the answer that we would get using the formula above by 2. Because the diameter is 5 the radius is 2.5. A=(3.14)(2.5^2)/2 A=(6.25)(3.14)/2 A=19.625/2 A=9.8125. I wrote it out long so that you could see the work.
