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

Perimeter and Area

At the beach, you have just built the greatest sand castle ever constructed. You do not want anyone else to destroy it. What are some things you might be able to do in order to protect it? 1) Draw lines all around the castle and write “Do Not Cross!” 2) Place sticks around the outside edge of the sand castle. 3) Build a moat around the castle.

Now, imagine that your parents have just bought you a new puppy. You must build a fence in order to keep the new puppy from running away. What information would you need to gather in order to be able to build this fence? 1)The shape of the fence 2) The length and width of the space to be fenced 3) The location of the fence 4) The cost of the fence

In both scenarios we have discussed situations in which something needs to be surrounded and in which we need to know the distance around the item (sand castle or yard) in order to successfully complete our tasks. Can you think of some other situations in which we would need to know the distance around an object or location? 1) Installing wallpaper border 2) Installing a fence 3) The distance around a track

In mathematics, we refer to this distance around an object as its perimeter. Today we will focus on the perimeter part of objective 4c.

It is necessary to measure the distance around the classroom. How would you do this? Then choose a couple of volunteers to pull a tape measure and begin measuring. We need to record the measurement of each wall and then add them together. You have discovered the distance around the classroom. What is the name for what we just measured?

Perimeter – the distance around a figure Perimeter is the measurement of distance around the outside of a figure. You will be exploring some different formulas to use to find the perimeter of various shapes. We are on page 90 in your notes. What can you tell me about the word formula for perimeter? The meaning of the word formula is a mathematical statement that uses numbers and/or symbols to express a relationship. In this lesson, you will be using formulas for perimeter and area. This means you will be substituting numbers in place of symbols to determine a perimeter and/or area.

Perimeter of Squares: Each student gets a geoboard and a rubber band. (If you pop your rubber band, you will lose it.) Watch me form a two-by-two square on the geoboard. Hold your boards up so I can assess if you have formed them correctly. Count the units around the outside edge.

You should count a total of 8 units around the outside edge. What you have found is the perimeter of the square. Form a three-by three square and count the units around the outside edge. The total is 12 units. Therefore the perimeter is 12. Form a four-by four square. You have found the perimeter of this square is 16 units.

Recordings: 1) Perimeter of a square with a side of length 2 units = 8 units 2) Perimeter of square with a side of length 3 units = 12 units 3) Perimeter of square with a side of length 4 units = 16 units

What relationship do you notice between the length of the side of the square and the perimeter? Explain your discoveries. The perimeter is always 4 times the length of the side of the square. Therefore, we arrive at the following formula for determining the perimeter of a square as P = 4s. Use the formula for the perimeter of a square to find the perimeter of each of the following: 1) Square with side length 3.5 inches 14 inches 2) Square with side length ½ mm 2 mm 3) Square with side length 5 cm 20 cm

Perimeter of Rectangles: This is how to form a rectangle on the geoboard that is 3 units long and 2 units wide. Form the same rectangle on your geoboards and hold them up. This is how to count the total number of units around the outside edge of the rectangle. The total distance around this rectangle is 10 units. This means the perimeter of the rectangle is 10 units.

Form a rectangle that is 4 units long and 3 units wide. Repeat the process with a rectangle that is 4 units long and 2 units wide. 1) Perimeter of a rectangle that is 3 units long and 2 units wide = 10 units 2) Perimeter of a rectangle that is 4 units long and 3 units wide = 14 units 3) Perimeter of a rectangle that is 4 units long and 2 units wide = 12 units

What relationship do you see between the dimensions of the rectangle and its corresponding perimeter? Explain your discoveries. If you add the two dimensions and then multiply by 2, you arrive at the perimeter. Perimeter of a Rectangle = 2 (l + w) or 2l +2w

Use the formula to find the solution to each of the following: Rectangle with length 5 inches and width 2 inches 14 inches A 6 cm by 4 cm rectangle 20 cm A rectangle that is 5.4 feet by 2.3 feet 15.4 feet

A 8 feet by 3 feet rectangle 22 feet A rectangle that is 9.7 cm by 3.1 cm 25.6 cm Rectangle with the length 12 m and width 4 32 m

Perimeter of Triangles and Any Polygon Form an octagon of their choice on the geoboards. It must have 8 sides. Students should sketch an exact copy of their octagons on their centimeter grid paper. Approximate the number of units on each side of the octagon and label it on your grid paper. If a length is a diagonal, students should estimate to the nearest tenth. Next, have students add or count the number of units around the outside edge of your figure. What you have just counted represents the perimeter of your octagon.

Repeat the procedure with a pentagon and a hexagon. Regardless of the shape of the polygon, the perimeter is always the distance around. For those polygons without a special formula, we simply add the lengths of the sides.

Fid the perimeter of a hexagon if all sides are equal to 3.5 centimeters. A hexagon has 6 sides.

Fid the perimeter of a decagon if all sides have a length of ½ inch. A decagon has 10 sides.

Fid the perimeter of a pentagon with sides of lengths 2.3, 1.5, 3, 1.5, and 7.

Independent Practice: Begin working handout #2 on perimeter in your JBHM binders. You will finish this handout for homework.

Closure: Respond to the following instructions: 1) Draw a rectangle on grid paper that has a perimeter of 24 units.