Warm Up

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Warm Up
Problem of the Day
Lesson Presentation
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Warm Up 1. What is the area of a figure made up
of a rectangle with length 12 cm and height 4 cm
and a parallelogram with length 12 cm and height
6 cm? 2. What is the area of a figure consisting
of a triangle sitting on top of a rectangle? The
triangle has a base of 12 in. and height of 9
in., and the rectangle has a base of 12 in. and
height of 5 in.
120 cm2
114 in2
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Problem of the Day If sixteen people sit, evenly
spaced, in a circle for story time, who sits
directly across from person 5?
person 13
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Learn to make a model to explore how area and
perimeter are affected by changes in the
dimensions of a figure.
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Additional Example 1 Changing Dimensions Find
how the perimeter and the area of the figure
change when its dimensions change.
1 inch
Draw a model of the two figures on graph paper.
Label the dimensions.
The original figure is a 4 ? 2 in. rectangle.
The smaller figure is a 2 ? 1 in. rectangle.
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Additional Example 1 Continued Find how the
perimeter and the area of the figure change when
its dimensions change.
Use the formula for perimeter of a rectangle.
Substitute for l and w.
2(4 2)
2(2 1)
Simplify.
2(6) 12
2(3) 6
The perimeter is 6 in.
The perimeter is 12 in.
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Additional Example 1 Continued Find how the
perimeter and the area of the figure change when
its dimensions change.
Use the formula for area of a rectangle.
A lw
Substitute for l and w.
8
2
Simplify.
The area is 8 in2.
The area is 2 in2.
The perimeter is divided by 2, and the area is
divided by 4.
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Check It Out Example 1 Find how the perimeter
and the area of the figure change when its
dimensions change.
1 inch
Draw a model of the two figures on graph paper.
Label the dimensions.
The original figure is 2 x 2 in. rectangle.
The larger figure is a 4 x 4 in. rectangle.
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Check It Out Example 1 Continued Find how the
perimeter and the area of the figure change when
its dimensions change.
Use the formula for perimeter of a rectangle.
Substitute for l and w.
2(2 2)
2(4 4)
Simplify.
2(4) 8
2(8) 16
The perimeter is 16 in.
The perimeter is 8 in.
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Check It Out Example 1 Continued Find how the
perimeter and the area of the figure change when
its dimensions change.
Use the formula for area of a rectangle.
A lw
Substitute for l and w.
4
16
Simplify.
The area is 4 in2.
The area is 16 in2.
The perimeter is multiplied by 2, and the area is
multiplied by 4.
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Additional Example 2 Application Draw a
rectangle whose dimensions are 4 times as large
as the given rectangle. How do the perimeter and
area change?
12 cm
3 cm
8 cm
2 cm
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Check It Out Example 2 Draw a rectangle whose
dimensions are 2 times as large as the given
rectangle. How do the perimeter and area change?
10 cm
5 cm
6 cm
3 cm
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Insert Lesson Title Here
Lesson Quiz
Find how the perimeter and area of the triangle
change when its dimensions change.
The perimeter is multiplied by 2, and the area is
multiplied by 4 perimeter 24, area 24
perimeter 48, area 96.