UNDERLYING SKILLS AND CONCEPTS:
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Use and$SSO\WKHDUHDDQGSHULPHWHUIRUPXODVIRUUHFWDQJOHVLQUHDOZRUOG
interpret formulas (e.g., area ! length " width or
DQGPDWKHPDWLFDOSUREOHPV)RUH[DPSOHILQGWKHZLGWKRIDUHFWDQJXODUURRPJLYHQWKH
A ! lw) to answer questions about quantities and their
DUHDRIWKHIORRULQJDQGWKHOHQJWKE\YLHZLQJWKHDUHDIRUPXODDVDPXOWLSOLFDWLRQ
relationships.
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basic facts;
meaning of variable;
multiplication
Use Formulas for Area
Area is the number of square units needed to cover a flat surface.
a
K
ey Ide
You can count squares to find the area.
w!2
s!2
l!4
The area is 8 square units
The area is 4 square units.
You can also use these formulas to find the area of rectangles and squares.
Rectangle:
A ! lw
1
Find the area of this rectangle.
A ! lw
A!6"4
A ! 24 square units
w ! 4 in.
l ! 6 in.
E x am p l E
2
Find the area of a square when s = 6 feet.
A!s"s
A!6"6
A ! 36 square units
s ! 6 in.
page 222
Chapter 19 – Lesson 3
D – © CSL Associates, Inc. All rights reserved.
E x am p l E
Square:
A!s"s
Name
P RAC T I C E
Find the area of each rectangle and square.
1.
w 4 ft
2.
3.
l 10 ft
l 7 ft
w 15 ft
28 square feet
4. l 15 in.
s 2 ft
150 square feet
5. l 24 ft
w 12 in.
4 square feet
6. s 10 in.
w 18 ft
180 square in.
7. l 23 ft
432 square ft
100 square in.
9. l 74 m
8. s 125 ft
w 52 m
w 17 ft
391 square ft
15,625 square ft
3848 square m
D – © CSL Associates, Inc. All rights reserved.
Solve each problem.
10. Charles is putting a fence in his
back yard for a dog run. He wants
the dog run to be 20 ft and 6 ft
wide. What is the area of the dog
run?
11. Carole bought a rug with an area
of 80 square feet. The rug is 8 feet
wide. How long is it?
120 square ft
Math
Reasoning
10 feet
Area
MR 1.2
12. Explain how the formula for the area of a square relates to the formula for
the area of a rectangle.
Since the length and width of a square are the same you
can substitute s for l and for w in the formula for the area of
a rectangle. Then A l w or A s s.
Chapter 19 – Lesson 3
page 223
MCX94.HW.CL.G4.FM&Lesson.v211
8/2/04
19:16
Page 150
Name
…at home!
P RAC T I C E
Find the area of each rectangle and square.
1.
w 3 ft
2.
3.
l 8 ft
l 9 ft
s 12 ft
w 13 ft
27 square feet
4. l 15 in.
104 square feet
6. s 10 in.
5. l 24 ft
w 12 in.
144 square feet
w 18 ft
180 square in.
7. l 2.3 ft
432 square ft
8. s 12.5 ft
w 1.7 ft
3.91 square ft
156.25 square ft
100 square in.
9. l 7.4 m
w 5.2 m
38.48 square m
10. Charles is putting a fence in his
back yard for a dog run. He wants
the dog run to be 20 ft long and 6
ft wide. What is the area of the
dog run?
11. Carole bought a rug with an area
of 80 square feet. The rug is 8 feet
wide. How long is it?
120 square ft
Math
Reasoning
10 feet
Area
MR 1.2
12. Explain how the formula for the area of a square relates to the formula for
the area of a rectangle.
Since the length and width of a square are the same you
can substitute s for l and for w in the formula for the area of
a rectangle. Then A l w or A s s.
page 150
Home Resource and Homework
Chapter 19 Lesson 3
D – © CSL Associates, Inc. All rights reserved.
Solve each problem.
MCX94TEG4Ch01_32.v8.5.2 2/26/01 19:03 Page 411
Name
P RAC T I C E
Find the area of each rectangle and square.
1.
w 4 ft
2.
3.
l 10 ft
l 7 ft
w 15 ft
28 square feet
4. l 15 in.
s 2 ft
150 square feet
5. l 24 ft
w 12 in.
4 square feet
6. s 10 in.
w 18 ft
180 square in.
7. l 23 ft
432 square ft
100 square in.
9. l 74 m
8. s 125 ft
w 52 m
w 17 ft
391 square ft
15,625 square ft
3848 square m
D – © CSL Associates, Inc. All rights reserved.
Solve each problem.
10. Charles is putting a fence in his
back yard for a dog run. He wants
the dog run to be 20 ft and 6 ft
wide. What is the area of the dog
run?
11. Carole bought a rug with an area
of 80 square feet. The rug is 8 feet
wide. How long is it?
120 square ft
Math
Reasoning
10 feet
Area
MR 1.2
12. Explain how the formula for the area of a square relates to the formula for
the area of a rectangle.
Since the length and width of a square are the same you
can substitute s for l and for w in the formula for the area of
a rectangle. Then A l w or A s s.
Chapter 19 – Lesson 3
Student Book Page
page 223
Name
…at home!
P RAC T I C E
Find the area of each rectangle and square.
1.
w 3 ft
2.
3.
l 8 ft
l 9 ft
s 12 ft
w 13 ft
27 square feet
4. l 15 in.
104 square feet
6. s 10 in.
5. l 24 ft
w 12 in.
144 square feet
w 18 ft
180 square in.
7. l 2.3 ft
432 square ft
8. s 12.5 ft
w 1.7 ft
3.91 square ft
156.25 square ft
100 square in.
9. l 7.4 m
w 5.2 m
38.48 square m
10. Charles is putting a fence in his
back yard for a dog run. He wants
the dog run to be 20 ft long and 6
ft wide. What is the area of the
dog run?
11. Carole bought a rug with an area
of 80 square feet. The rug is 8 feet
wide. How long is it?
120 square ft
Math
Reasoning
10 feet
Area
MR 1.2
12. Explain how the formula for the area of a square relates to the formula for
the area of a rectangle.
Since the length and width of a square are the same you
can substitute s for l and for w in the formula for the area of
a rectangle. Then A l w or A s s.
page 150
Home Resource and Homework
Chapter 19 Lesson 3
D – © CSL Associates, Inc. All rights reserved.
Solve each problem.