Skill: Calculate the area of trapezoids

A trapezoid has two parallel sides, called the bases. Its area is found by averaging the lengths of the bases and multiplying by the perpendicular height:

$$A=\frac{1}{2}(b_1+b_2)h$$

The height is the straight-line distance between the parallel bases. It is not necessarily the length of either slanted side.

Example: Find the area of a trapezoid with bases of $8$ cm and $14$ cm and a height of $5$ cm.

1. Identify the measurements:

$$b_1=8,\qquad b_2=14,\qquad h=5$$

2. Substitute them into the formula:

$$A=\frac{1}{2}(8+14)(5)$$

3. Add the base lengths:

$$A=\frac{1}{2}(22)(5)$$

4. Multiply:

$$A=11\cdot 5=55$$

Therefore, the area of the trapezoid is

$$\boxed{55\text{ cm}^2}$$

The answer is in square centimeters because area measures the amount of surface inside the trapezoid.