Skill: Calculate the area of parallelograms

The area of a parallelogram is the amount of space inside it. Use the formula

$$A=b\times h$$

where:

• $b$ is the length of the chosen base.
• $h$ is the perpendicular height, the straight-up-and-down distance between the parallel sides.

The slanted side is not usually the height. The height must meet the base at a right angle.

Example: Find the area of a parallelogram with a base of $8$ cm and a perpendicular height of $5$ cm.

1. Identify the base and height:

$$b=8\text{ cm}, \qquad h=5\text{ cm}$$

2. Substitute the values into the formula:

$$A=b\times h$$ $$A=8\times5$$

3. Multiply:

$$A=40$$

4. Write the answer in square units:

$$\boxed{40\text{ cm}^2}$$

You can also see why the formula works by cutting off the triangle on one slanted side and moving it to the other side. This makes a rectangle with the same base and height, so its area is still $b\times h$.