Determining perimeter

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The students learn to determine the perimeter of various shapes.

CCSS.Math.Content.4.MD.A.3

Students will be able to determine the perimeter of a shape.

On the interactive whiteboard there is a shape with squares around it. The students determine the perimeter of the shape by counting the squares.

You explain that when you want to determine the perimeter of a rectangle, you first look at the length of the sides. Then you add the lengths of the sides together. You can also determine the perimeter of a rectangle by doing the length times two and also the width times tow. Then you add these outcomes together. After this you show how you can determine the perimeter of a different shape. For this you also must look at the lengths of the sides and then add them all together. You can determine the perimeter of the following two shapes together with the students, or have them determine the perimeters on their own. You can show the answers by erasing the covers. After this there is a story problem on the whiteboard that you can discuss with the students. Finally you show how you can determine the length of the ribbon around the present. You explain that you can first determine the length on top by adding the length and width together. You multiply this outcome by two, because the length of the ribbon on the bottom is the same. Then you add the length of the ribbon on the side four times, for the height of the present. Finally, you add all these outcomes together for your answer.

To check whether the students can determine the perimeter of a shape, you can ask the following questions:

- How can you determine the perimeter of a rectangle?

- What do you do if the shape is not a rectangle?

- How do you determine the length of a ribbon around a present?

The students test their understanding of determining perimeter through ten exercises. In some of the exercises they have visual support in the form of a shape with the sides labeled, and others are story problems.

You repeat the learning goal and its importance. Next there is a map of a zoo on the interactive whiteboard. For each enclosure it is stated which animal is there and how long the sides of the enclosure are. The students determine the perimeter of the different enclosures. You can have the students work in groups and then explain to one another how they determined the perimeter of the different areas.

When students have difficulty with this learning goal, they can use shapes with squares around them to see how the perimeter of an object is determined. For the story problems you can draw shapes and write the measurements of the sides as a visual support.

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