The rectangle method
Sponsored Links
This presentation is the property of its rightful owner.
1 / 35

The Rectangle Method PowerPoint PPT Presentation


  • 91 Views
  • Uploaded on
  • Presentation posted in: General

The Rectangle Method. Finding Area of Triangles and Parallelograms. Find something in the room shaped like: a hexagonal prism a cylinder a quadrangle a cube. A 30 Second Look-See. Read the top of page 315

Download Presentation

The Rectangle Method

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


The Rectangle Method

Finding Area of Triangles and Parallelograms


Find something in the room shaped like:

  • a hexagonal prism

  • a cylinder

  • a quadrangle

  • a cube

A 30 Second Look-See


  • Read the top of page 315

  • Your job will be to think of ways to find the areas of the triangles – I am not interested in the answer.

    I am interested in the methods you

    and your partner discover.

Math Journal page 315


  • This is called the rectangle method because rectangles are used to surround the figure or parts of the figure. All of the areas that are calculated are either areas of rectangles or of triangular halves of rectangular regions.

Rectangle Method


Add the Parts


Split this triangle up into two different triangles, both with right angles, count the units that cover each and find the sum of the two parts.


12 units

3 units

Split this triangle up into two different triangles, both with right angles, count the units that cover each and find the sum of the two parts.


12 units

3 units

3 units + 12 units = 15 units


Using the rectangle method, draw a rectangle around each of these triangles.


What observation can you make about these shapes and the shaded regions?


These triangles and ½ of the area of the rectangle. How will this information help us to find the area of the triangles?


12 units

3 units

These triangles and ½ of the area of the rectangle. How will this information help us to find the area of the triangles?


Find the area of this triangle with your table.


Find the area of this triangle with your table.


9 units

15 units

Find the area of each rectangle by multiplying the base x height.


9 ÷ 2 =

4 ½ units

15 ÷ 2 =

7 ½ units

To find the area of the triangles divide the area of the rectangles by 2 or find the value of ½ the rectangle.


4 ½ units

7 ½ units

4 ½ + 7 ½ = 12 units


  • Return to page 315.

  • Find the area of triangle #1 by splitting the triangle into two right triangles. Use the add the parts method to find the area of the complete triangle.

Review your work


To find the area, draw two right angles around the triangle to create a rectangle.


Find the area of the yellow and blue triangles. Use the rectangle method mentally.


7 ½ units

5 units

Find the area of the yellow and blue triangles. Use the rectangle method mentally.


The sum of the yellow and blue triangles is 12 ½ units.


To find the area of the red triangle, find the area of the rectangle and subtract the 12 ½ units of the blue and yellow triangles.

The difference will be the area of the red triangle.


15 units – 12 ½ units = 2 ½ units.

If the yellow triangle is 7 ½ units , and the blue triangle is 5 units, does it make sense that the red triangle is 2 ½ units?


Review your work


Area of a Parallelogram


Use what you know to determine a strategy to find the area of this shape.


Determine the areas of the three shapes and add the parts.


1 x 6 = 6

6 ÷ 2 = 3

= 3 units

Determine the areas of the three shapes and add the parts.


1 x 6 = 6

6 ÷ 2 = 3

= 3 units

Determine the areas of the three shapes and add the parts.


6 x 4 = 24 units

Determine the areas of the three shapes and add the parts.


24 units

= 3 units

= 3 units

3 + 3 + 24 = 30 units


  • Return to page 315.

  • Find the area of triangle #3 by splitting the parallelogram into two right triangles and a rectangle. Use the add the parts method to find the area of the complete parallelogram.

Review your work


  • Math Journal page 316

Practice with a Partner


  • Math Sheet p. 126

Practice on Your Own


  • Login