The part of a circle that is in this problem is a semi-circle, which is exactly half of a circle.
That means you can do the area of a circle (pi * r^2) and half it to find the area of the semi-circle.
You've also been told to approximate pi with 3.14.
So first, work out the area of the rectangle (18 * 6 = 108)
Now, time for the semi-circle. The diameter of the semi-circle is the same as the length of the rectangle (6 cm), hence you can half it to find the radius (3 cm).
Now just do 3.14 * 3^2 (which is the same as 3.14 * 9) and then half it.
For partial circles, first imagine that there is an entire circle. To find the area of a cicle, you use the formula A=pi*r^2 or A=3.14*r^2. Then determine how much of a circl you have so you can alter the formula. Since you have a semicircle, or half a circle, simply divide the formula in half:
A=(3.14*r^2)/2
Then plug in your radius to find the area. So for this problem you do: A=(3.14*3^2)/2 A=28.26/2 A=14.13 is the area of the semicircle
The measure of an arc is the same as the measure of the central angle it subtends. The arc is marked 153°. The central angle (?°) has that same measure.