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interpret formulas (e.g., area ! length " width or
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relationships.
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UNDERLYING SKILLS AND CONCEPTS:
basic facts;
meaning of variable;
multiplication
Solve Problems Using Formulas
a
K
ey Ide
When you solve problems, use the 4-step Problem-Solving Plan.
When you get to Step 3, try using a formula to solve the problem.
Perimeter
Rectangle: P ! 2 " l # 2 " w
Square: P ! 4 " s
Area
Rectangle: A ! l " w
Square: A ! s " s
Distance Formula: d ! r " t
E x am p l E
1. What do you need to
find out?
The amount of chicken wire needed for a fence.
2. What information can
you use?
The garden is 24 feet long and 6 feet wide.
3. How can you solve the
problem?
Use can use a formula. First choose which
formula you need to use. Since they are putting
the chicken wire around the garden you want to
find perimeter.
P!2"l#2"w
P ! 2 " 24 # 2 " 6
P ! 48 # 12
P ! 60
They need 60 feet of chicken wire.
4. How can you check
your answer?
Since you found perimeter, you can check by
adding the lengths of the 4 sides.
24 + 24 + 6 + 6 = 60
The answer checks.
page 224
Chapter 19 – Lesson 4
D – © CSL Associates, Inc. All rights reserved.
Kim’s class planted a vegetable garden. The garden is rectangular.
It is 24 feet long and 6 feet wide. The want to put a chicken-wire fence
around it. How much chicken wire do they need?
Name
P RAC T I C E
Solve each problem using a formula.
1. Judy is putting fringe around a
scarf. The scarf is a square. Each
side is 18 inches long. How much
fringe does she need?
2. Judy’s scarf is a square. Each side is
18 inches long. What is the area of
the scarf?
72 inches
3. Judy rode her bike to the store. She
rides at a rate of 1 block a minute.
She rode for 10 minutes. How far
did she ride?
324 square inches
4. Judy’s mother drove to the mall.
She drove 25 miles per hour. It
took her 2 hours. How far did she
drive?
10 blocks
D – © CSL Associates, Inc. All rights reserved.
50 miles
Math
Reasoning
Problems Using Formulas
MR 1.1
5. What formula would you use to find the amount of framing you need to
put around a rectangular picture? Explain.
I would use P = 2 x l + 2 x w since the frame would go
around the picture like a perimeter.
Chapter 19 – Lesson 4
page 225
MCX94.HW.CL.G4.FM&Lesson.v211
8/2/04
19:16
Page 152
Name
…at home!
P RAC T I C E
Solve each problem using a formula.
1. Helen is putting lace around a
collar. The collar is a square. Each
side is 16 inches long. How much
lace does she need?
2. Jack’s scarf is a rectangle. The scarf
is 30 inches long and 8 inches
wide. What is the area of the scarf?
l 30 in.
s 16 in.
3. James rode his scooter to the store.
He rides at a rate of 2 blocks a
minute. He rode for 5 minutes.
How far did he ride?
240 square inches
4. April’s mother drove to the mall.
She drove 35 miles per hour. It
took her 2 hours. How far did she
drive?
10 blocks
70 miles
Math
Reasoning
Problems Using Formulas
MR 1.1
5. What formula would you use to find the amount of framing you need to put
around a kitchen window? Explain.
I would use P 2 l 2 w since the frame would go
around the window like a perimeter.
page 152
Home Resource and Homework
Chapter 19 Lesson 4
D – © CSL Associates, Inc. All rights reserved.
64 inches
MCX94TEG4Ch01_32.v8.5.2 2/26/01 19:03 Page 415
Name
P RAC T I C E
Solve each problem using a formula.
1. Judy is putting fringe around a
scarf. The scarf is a square. Each
side is 18 inches long. How much
fringe does she need?
2. Judy’s scarf is a square. Each side is
18 inches long. What is the area of
the scarf?
72 inches
324 square inches
3. Judy rode her bike to the store. She
rides at a rate of 1 block a minute.
She rode for 10 minutes. How far
did she ride?
4. Judy’s mother drove to the mall.
She drove 25 miles per hour. It
took her 2 hours. How far did she
drive?
10 blocks
D – © CSL Associates, Inc. All rights reserved.
50 miles
Math
Reasoning
Problems Using Formulas
MR 1.1
5. What formula would you use to find the amount of framing you need to
put around a rectangular picture? Explain.
I would use P = 2 x l + 2 x w since the frame would go
around the picture like a perimeter.
Chapter 19 – Lesson 4
Student Book Page
page 225
Name
…at home!
P RAC T I C E
Solve each problem using a formula.
1. Helen is putting lace around a
collar. The collar is a square. Each
side is 16 inches long. How much
lace does she need?
2. Jack’s scarf is a rectangle. The scarf
is 30 inches long and 8 inches
wide. What is the area of the scarf?
l 30 in.
s 16 in.
3. James rode his scooter to the store.
He rides at a rate of 2 blocks a
minute. He rode for 5 minutes.
How far did he ride?
240 square inches
4. April’s mother drove to the mall.
She drove 35 miles per hour. It
took her 2 hours. How far did she
drive?
10 blocks
70 miles
Math
Reasoning
Problems Using Formulas
MR 1.1
5. What formula would you use to find the amount of framing you need to put
around a kitchen window? Explain.
I would use P 2 l 2 w since the frame would go
around the window like a perimeter.
page 152
Home Resource and Homework
Chapter 19 Lesson 4
D – © CSL Associates, Inc. All rights reserved.
64 inches