Warm Up

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Warm Up
Problem of the Day
Lesson Presentation
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Warm Up 1. What is the perimeter of a square
with side lengths of 15 in.? 2. What is the
perimeter of a rectangle with length 16 cm and
width 11 cm?
60 in.
54 cm
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Problem of the Day Two wibbles equal four
wabbles, and eight wabbles equal two bibbles. If
a square has a perimeter of 16 wibbles, what is
its area in square bibbles?
4 square bibbles
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Learn to estimate the area of irregular figures
and to find the area of rectangles and
parallelograms.
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Insert Lesson Title Here
Vocabulary
area
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The area of a figure is the amount of surface it
covers. We measure area in square units.
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Additional Example 1 Estimating the Area of an
Irregular Figure Find the area of the rectangle.
Count full squares 19 red squares.
Count almost-full squares 9 blue squares.
Count squares that are about half-full 4 green
squares 2 full squares.
Do not count almost empty yellow squares.
Add. 19 9 2 30
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Check It Out Example 1 Estimate the are of the
figure.
Count full squares 11 red squares.
Count almost-full squares 5 green squares.
Count squares that are about half-full 4 blue
squares 2 full squares.
mi2
Do not count almost empty yellow squares.
Add. 11 5 2 18
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Additional Example 2 Finding the Area of a
Rectangle Find the area of the figure.
Write the formula.
15 in.
Substitute 15 for l.
9 in.
Substitute 9 for w.
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Check It Out Example 2 Find the area of the
figure.
Write the formula.
13 in.
Substitute 13 for l.
7 in.
Substitute 7 for w.
The area is about 91 in2.
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You can use the formula for the area of a
rectangle to write a formula for the area of a
parallelogram. Imagine cutting off the triangle
drawn in the parallelogram and sliding it to the
right to form a rectangle.
The area of a parallelogram bh.
The area of a rectangle lw. The base of the
parallelogram is the length of the rectangle. The
height of the parallelogram is the width of the
rectangle.
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Additional Example 3 Finding the Area of a
Parallelogram Find the area of the parallelogram.
Write the formula.
1
1 ft
4
1
2 ft
2
Multiply.
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Check It Out Example 3 Find the area of the
parallelogram.
Write the formula.
Multiply.
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Additional Example 4 Recreation
Application Jessika is going to tile a kitchen
that measures 13 ft by 17 ft. Some floor space is
taken up by an island that measures 3 ft by 6 ft.
How much area remains to be tiled in the kitchen?
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floor area
kitchen area to be tiled
island
Substitute for l and w in A lw.
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(13 17)
(3 6)
n
Use the order of operations.
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Check It Out Example 4 Miguel is going to
landscape his backyard that measures 16 ft by 11
ft. Some of the backyard space is taken up by a
built-in BBQ that measures 2 ft by 4 ft. How much
area remains to be landscaped?
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backyard area
landscaped area
BBQ
Substitute for l and w in A lw.
(16 11)
(2 4)
n
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Use the order of operations.
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Insert Lesson Title Here
Lesson Quiz
Find the area of each figure. 1. 2.
3. What is the area of a parallelogram with
base 16 in. and height 10 in.? 4. A square fish
pond that is 6 ft long is surrounded by a square
walk that is 18 ft long. What is the area covered
by the walk?
4.5 m
9.2 m