Section 10.1 – Area: Parallelograms

pages 522 - 526

The area of a figure is the number of square units it encloses. The rectangle outlined in red encloses 8 square units, each with area 1 cm2 (1 square centimeter). So, the area of the rectangle is 8 cm2.

You can use the formula A = bh to find the area of a rectangle, where b is the length of one side and h is the length of the other. For the rectangle above, A = 4 • 2 = 8. So, the area is 8 cm2.

When you find area, the dimensions must be in the same unit.

Example 1:

Find the area of the marching band's rectangular banner. step 1: Change the units so that they are the same.

step 2: Find the area.

The area of the banner is 21 ft2.

Check Understanding:

a. Find the area of the rectangle.

b. Find the area of the rectangle.

A rectangle is a special kind of parallelogram. The formula for the area of a parallelogram follows from the formula for the area of a rectangle. The height h of a parallelogram is the length of an altitude.

An altitude is a line segment perpendicular to the line containing a base of the figure and drawn from the side opposite that base.

Area of a Parallelogram

The area of a parallelogram is the product of any base length b and the corresponding height h.

Example 2: Finding area of a parallelogram

Check Understanding

a. Find the area of the parallelogram.            

b. Find the area of the parallelogram.                     

Homeworkpages 524 - 525 #s 1-15, 26-29

– DRAW DIAGRAMS and– write problems and answers, EXCEPT

for word problems and multiple-choice problems

– SHOW ALL WORK!– failure to write problems and/or show

work will result in either receiving partial or no credit