Download Write and Evaluate Algebraic Expressions

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Use a letter
to represent an unknown number; write and
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evaluate simple algebraic expressions in one variable by
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UNDERLYING SKILLS AND CONCEPTS:
add, subtract, multiply, and divide with
whole numbers
substitution.
Write and Evaluate Algebraic Expressions
An expression that contains a variable is an algebraic expression.
A variable is a letter that is used to represent a number.
To evaluate an algebraic expression, replace the variable with a given
number. To evaluate the expression, do the computation.
1
The cost of an adult movie ticket is $5 more than the
cost of a student ticket, s $ 5.
If a student ticket costs $3.50, what is the cost
of an adult ticket?
Step 1: Ask: What do you know?
You know that the adult ticket costs
$5 more than s, the student ticket.
You know that a student ticket costs $3.50.
This is easy!
When I know the value
of the variable,
I can do the math.
Step 2: Write an expression.
So, an adult ticket costs s $ $5.
Step 3: Evaluate s $ 5 when s " $3.50.
Hint: Substitute $3.50 for s.
$3.50 $ $5 " $8.50
So, an adult ticket costs $8.50.
E x am p l E
2
E x am p l E
Evaluate y ! 15 for y " 32.
Evaluate 7 # n for n " 8.
y ! 15
Substitute 32 for y.
7#n
Substitute 8 for n.
32 ! 15 " 17
page 114
3
7 # 8 " 56
Chapter 10 – Lesson 3
E – © CSL Associates, Inc. All rights reserved.
E x am p l E
Name
P RAC T I C E
Evaluate each expression.
1. n 9 for n 20
2. 15 y for y 2
11
17
3. 4a for a 10
n
4. 4 when n 32
40
8
5. n2 when n 5
6. s 17 when s 12
25
29
Write an expression.
7. a number decreased by 5
8. 5 increased by a number
n5
5n
9. 5 times a number
10. the quotient of a number and 5
5n
n
5 or n 5
E – © CSL Associates, Inc. All rights reserved.
11. a number increased by 5
n5
12. 15 decreased by a number
15 n
Write an expression for each relationship.
13. The number of inches in f feet.
12 f or 12 f
14. The number of minutes in h hours.
15. The number of sides in s squares.
4s
16. A raise of $2 on a salary, a.
a2
60h
Math
Reasoning
Equation Riddles
MR 2.2
What numbers can you substitute for n to make each equation true?
17. n n n n
18. n 3 2n
Chapter 10 – Lesson 3
0 0 0 0 so n 0 or 2 2 2 2 so n 2
3 3 2 3 so n 3
page 115
MCX94.HW.CL.G5.FM&Lesson.v211
8/2/04
18:02
Page 78
Name
…at home!
P RAC T I C E
Evaluate each expression.
1. n 8 for n 20
2. 15 y for y 4
20 8 12
3. 3a for a 10
3a 3 10 30
5. n2 when n 6
15 4 19
n
4. when n 40
4
40
10
4
6. s 17 when s 15
n2 62 36
15 17 32
Write an expression.
7. a number decreased by 7
8. 8 increased by a number
n7
8n
9. 8 times a number
10. the quotient of a number and 6
8 n 8n
12. 12 decreased by a number
n8
12 n
Write an expression for each relationship.
13. The number of feet in y yards.
3 y or 3 y
14. The number of hours in d days.
15. The number of sides in p pentagons.
5p
16. A raise of $4 on a salary, a.
a4
24d
Math
Reasoning
Equation Riddles
MR 2.2
What numbers can you substitute for n to make each equation true?
17. n n n 3
18. n 5 2n
page 78
n n 1, so 1 n 3, so n 4
5 5 2 5 so n 5
Home Resource and Homework
Chapter 10 Lesson 3
E – © CSL Associates, Inc. All rights reserved.
11. a number increased by 8
n6
MCX94TEG5CH01_32.v7.4.2 2/24/01 19:45 Page 213
Name
P RAC T I C E
Evaluate each expression.
1. n 9 for n 20
2. 15 y for y 2
11
17
3. 4a for a 10
n
4. when n 32
4
40
8
5. n2 when n 5
6. s 17 when s 12
25
29
Write an expression.
7. a number decreased by 5
8. 5 increased by a number
n5
5n
9. 5 times a number
10. the quotient of a number and 5
5n
n
5 or n 5
E – © CSL Associates, Inc. All rights reserved.
11. a number increased by 5
n5
12. 15 decreased by a number
15 n
Write an expression for each relationship.
13. The number of inches in f feet.
12 f or 12 f
14. The number of minutes in h hours.
15. The number of sides in s squares.
4s
16. A raise of $2 on a salary, a.
a2
60h
Math
Reasoning
Equation Riddles
MR 2.2
What numbers can you substitute for n to make each equation true?
17. n n n n
18. n 3 2n
Chapter 10 – Lesson 3
0 0 0 0 so n 0 or 2 2 2 2 so n 2
3 3 2 3 so n 3
Student Book Page
page 115
Name
…at home!
P RAC T I C E
Evaluate each expression.
1. n 8 for n 20
2. 15 y for y 4
20 8 12
3. 3a for a 10
3a 3 10 30
5. n2 when n 6
15 4 19
n
4. 4 when n 40 40
10
4
6. s 17 when s 15
n2 62 36
15 17 32
Write an expression.
7. a number decreased by 7
8. 8 increased by a number
n7
8n
9. 8 times a number
10. the quotient of a number and 6
8 n 8n
12. 12 decreased by a number
n8
12 n
Write an expression for each relationship.
13. The number of feet in y yards.
3 y or 3 y
14. The number of hours in d days.
15. The number of sides in p pentagons.
5p
16. A raise of $4 on a salary, a.
a4
24d
Math
Reasoning
Equation Riddles
MR 2.2
What numbers can you substitute for n to make each equation true?
17. n n n 3
18. n 5 2n
page 78
n n 1, so 1 n 3, so n 4
5 5 2 5 so n 5
Home Resource and Homework
Chapter 10 Lesson 3
E – © CSL Associates, Inc. All rights reserved.
11. a number increased by 8
n6