Problem #DES-2

Problem

Today we will solve some problems about finding areas of geometric figures. All you need to know in order to solve every problem in this set is: to calculate the area of a triangle we multiply the length of a side by the length of a height to that side and divide by $2$, namely:$\frac{1}{2}AB\times CD$, as for rectangle we just multiply two adjacent sides ($EF\times GF$), and when we have a circle we calculate the area by $\pi r^2$, where $r$ is the radius of the circle.