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Module 3 Lesson 1 Investigating Perimeter and Area Formulas.
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After this lesson you will be able to: Know the formula and how to find the perimeter of a rectangle. Know the formula and how to find the area of a rectangle. Lesson Objective
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What do you notice about this rectangle?
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Did you notice that one side is 4 and the other is 6?
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Did you know that the 4 represents the width?
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Did you know that the 6 represents the length?
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If I were to walk along the outside of this rectangle how many units would I travel?
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Did you get 20? 4 6
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What would this be called? 4 6
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The Perimeter 4 6
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Now let’s look at the squares inside of the rectangle. What do these represent?
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The squares represent the area! How could I find the area for this rectangle?
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We could count each individual square.
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We could count each individual square and get 24. 12 3 7 11 5 6 8 4 9 10 12 1314 15 16 17 18 19202122 23 24
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Let’s try finding the Perimeter and Area of this rectangle. What do I need to know to get the perimeter?
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Let’s try finding the Perimeter and Area of this rectangle. The length and width!
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Let’s try finding the Perimeter and Area of this rectangle. What is the length of this rectangle?
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Let’s try finding the Perimeter and Area of this rectangle. Now what is the width of this rectangle? 8
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Let’s try finding the Perimeter and Area of this rectangle. What do I do to find the perimeter? 8 3
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Let’s try finding the Perimeter and Area of this rectangle. We need to add up all the sides! 8 3 8 3
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Let’s try finding the Perimeter and Area of this rectangle. Does it matter the order in which I add the numbers? 8 3 8 3
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Let’s try finding the Perimeter and Area of this rectangle. 8 + 3 = 11; 11 + 8 = 19; 19 + 3 = 22 8 + 8 = 16; 3 + 3 = 6; 16 + 6 = 22 8 + 3 = 11; 8+ 3 = 11; 11 + 11 = 22 8 3 8 3
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Can you think of an easier way to find the perimeter? 8 + 3 = 11; 11 + 8 = 19; 19 + 3 = 22 8 + 8 = 16; 3 + 3 = 6; 16 + 6 = 22 8 + 3 = 11; 8+ 3 = 11; 11 + 11 = 22 8 3 8 3
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Can you think of an easier way to find the perimeter? 8 + 3 = 11; 11 + 8 = 19; 19 + 3 = 22 8 + 8 = 16; 3 + 3 = 6; 16 + 6 = 22 8 + 3 = 11; 8+ 3 = 11; 11 + 11 = 22 8 3 8 3 We could multiply instead of adding!
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Can you think of an easier way to find the perimeter? 8 + 8 = 16; 3 + 3 = 6; 16 + 6 = 22 We could do (8 x 2) + (3 x 2). This formula is: 2L + 2W. 8 3 8 3
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Can you think of an easier way to find the perimeter? 8 + 3 = 11; 8+ 3 = 11; 11 + 11 = 22 We could do (8 + 3) x 2 This formula is: 2 x (L + W) 8 3 8 3
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You have discovered the formulas for finding the perimeter! 2 x (L + W) 2L + 2W 8 3 8 3
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Now let’s look at the area! How do we find the area? 8 3 8 3
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Now let’s look at the area! We can count all of the boxes. 8 3 8 3
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Now let’s look at the area! 8 3 8 3 1 23 4 5 6 7 8 9 10 11 12 13 1415 16 17 18 19 20 21 22 23 24
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Now let’s look at the area! 8 3 8 3 1 23 4 5 6 7 8 9 10 11 12 13 1415 16 17 18 19 20 21 22 23 24 Is there a quicker way to find the area of the rectangle.
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What if we skip count by 8? 8 3 8 3 1 23 4 5 6 7 8 Is there a quicker way to find the area of the rectangle.
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What if we skip count by 8? 8 3 8 3 1 23 4 5 6 7 8 Is there a quicker way to find the area of the rectangle. 9 10 11 12 13 1415 16
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What if we skip count by 8? 8 3 8 3 1 23 4 5 6 7 8 Skip counting is the same as… 9 10 11 12 13 1415 16 17 18 19 20 21 22 23 24
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What if we skip count by 8? 8 3 8 3 1 23 4 5 6 7 8 Skip counting is the same as… Multiplying! 9 10 11 12 13 1415 16 17 18 19 20 21 22 23 24
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Area Formula! We can multiply 8 x 3 and get 24. The formula for area is L x W 8 3 8 3
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Let’s try out the formulas! Let’s use the formulas we just learned to find the perimeter and area of the following rectangle.
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First we need to find… Before we can use the formulas, we need to find the L and W.
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First we need to find… Before we can use the formulas, we need to find the L and W. The L is 4 4
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First we need to find… Before we can use the formulas, we need to find the L and W. The L is 4 The W is 4 4 4
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First we need to find… Before we can use the formulas, we need to find the L and W. The L is 4 The W is 4 Let’s find the perimeter 4 4
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Let’s find the Perimeter 4 4 Use the formula you want and solve. 2 x (L + W) 2L + 2W
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Let’s find the Perimeter 2 x (L + W) (2 x 4) + (2 x 4) = 8 + 8 = 16 2 x (4 + 4) = 2 x 8 = 16 2L + 2W
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Now let’s find the area. 4 4 Use the formula and solve. L x W
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Now let’s find the area. 4 4 L x W 4 x 4 = 16
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Now it’s your turn! Find the Perimeter and Area of the following rectangles 3 7 5 6
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3 7 Perimeter: 20 Area: 21
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Now it’s your turn! Find the Perimeter and Area of the following rectangles 5 6 Perimeter: 22 Area: 30
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