PowerPoint created by Parsheena Berch Resource: JBHM material Pictures: Google Images

Perimeter and Area

So far we have learned how to find perimeter of any polygon and the area of squares and rectangles. How do you do each of these? Today, we will find area of other polygons.

Area Formula for Triangles Triangles: A =1/2 bh The base and height must be perpendicular to each other. Geoboards. Create a 2 x 2 square How many squares did it take? 4 What does this tell us about the area of this square? It is 4 units squared. Next, create two right triangles with one side having a length of 3 and another having a length of 2. Once you have made the first triangle, make another triangle connected to the first one to form a rectangle. What do you notice about the area of each of the triangles? Point out to the class that the two triangles make a rectangle with an area of 6 squared units.

Model a triangle with two sides equal to 5 Model a triangle with two sides equal to 5. Have them make another triangle connected to the first forming a square. What do you notice about the area of each of the triangles. Point out to the class that the two triangles make a square with an area of 25 squared units. The formula used to find the area of a triangle is A =1/2 bh. There are triangles in retangles and squares. We use the formula A =1/2 bh, because a triangle’s space is in fact half of that of a rectangle or square.

Find the area of the triangles described: A triangle with a side of length 6 and 4.

A triangle with a side of length 4 and 7

Use your geoboard to create a triangle that has a side length of 2 and a side length of 3. what is the are of the triangle?

Use your geoboard to create a triangle that has a length of 4 and a base of 5.

Find the area of a triangle with a side length of 5 and 6.

Find the area of a triangle with a side length of 12 and 3.

Area Formula for Parallelograms Any side of the parallelogram can be called its base. The length of a segment drawn from the opposite side of the parallelogram and perpendicular to the base is called the height.

Grid paper Using a ruler, create a parallelogram, sketch in the height from one vertex perpendicular to a base. Cut off the triangle formed and attach it to the other side with tape. What type of quadrilateral have you created? (Rectangle) Based on your discovery, what formula would we create for finding the area of a parallelogram? A = bh

Use the formula to find the area of a parallelogram with a base of 4 feet and a height of 2 feet.

Find the area of a parallelogram with a base of length9 inches and a height of length 7 inches.

Find that area of the following parallelogram.

Use the formula for finding the area of a parallelogram to find the area of this parallelogram. 4.25 yd 4.7 yd

Independent Practice: (DOK 2) Apply one of these formulas to find the area of a rectangle with a length of 5 cm and width of 3 cm. give the answer in square cm. 3cm 5cm

Determine the area of the following triangle. 7.5 in 8 in

Determine the area of a square with sides that have a length of 8 feet. Use the formula to find the area of a parallelogram with a base of 4 feet and a height of 2 feet. Apply the formula to find the area of a triangle that has a base of 8 cm and a height of 4 cm.

Closure: Make up a word problem in which you would need to find the perimeter or make up a word problem in which you would need to find the area. Share some of your ideas with the class.