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Recognize Area as Additive

3.MD.7
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Aligned To Common Core Standard:

Grade 3 Measurement - 3.MD.7

How to Determine the area of irregular rectangular shapes? A rectangle is one of the four basic two-dimensional shapes in geometry. Mathematics has a formula for calculating the area of a rectangular. All you need are the dimensions of the two sides adjacent sides of the triangle. When you have these two dimensions you can easily calculate the area using the following formula; Area of Rectangle=Length x Width - What do you do when you get an irregular rectangle; Here is how you can calculate the area of an irregular rectangle; Method 1: When you complete the missing sides, you see it resembles a square. Step 1: Area of large square=30x30=900in2 Step 2: Area of the white rectangle=10x18=180in2 Step 3: Subtract the area of the white rectangle from that of the large square Area of required shape=900-180=720in2 Method 2: You can divide the irregular rectangle into two smaller rectangles. If you have a irregular set of shapes marker area A-B-C. Step 1: Calculate the area of the larger part marked "A." Step 2: Calculate the area of the second part. Step 3: Add both the areas to determine the total area of the required shape. This collection of worksheets helps students understand that area can be considered a collective.

Printable Worksheets And Lessons


  • Area of Split Rectangles Step-by-step Lesson- Take a figure and break into 2 rectangles to help you find the area of the figure.

  • Guided Lesson - We start to look at the actual applications of this skill to the real world. Home contractors do this everyday.

  • Guided Lesson Explanation - I use outlines to show you how to break up area into digestible parts to work with.

  • Practice Worksheet - I did a three-three-three method here. Three simple word problems, three slightly involved problems, and three visual based problems.

  • Matching Worksheet - Match the word problems or the figures to their calculated area.



  • Homework Sheets

    Students will usually have the option to break the shape up in two directions.

    • Homework 1- We know how to find the area of a rectangle. What if we could make this into 2 rectangles? If we added the area of the two rectangles, we would have the total area of the figure.
    • Homework 2- Let's break the figure into two rectangles. Then we just need to find the area of each rectangle and add the areas together.
    • Homework 3- Abe is building a uniquely shaped deck. The contractor charges $9 per square foot. How much will it cost Alien for this deck?



    Practice Worksheets

    Always encourage students to color in the shapes or at least draw a line, like I do.

    • Practice 1- Abe is building a uniquely shaped deck. The contractor charges $12 per km. How much will it cost Abe for this deck?
    • Practice 2- Find the area of the figures.
    • Practice 3- Find the area of the figure below.



    Math Skill Quizzes

    It takes forever to double check the answer keys on these.