Write and Evaluate Expressions GOAL: By the end of this lesson, we will ALL be able to write and evaluate addition and subtraction expressions

Write and Evaluate Expressions

GOAL: By the end of this lesson, we will ALL be able to write and evaluate

addition and subtraction expressions

Review Identity Property:

Associative Property:

Commutative Property:

0 Ex: 5 + 0 = 5

( )

Ex: (1+2) + 3 = 1 + (2+3) Flip-Flop; any

order Ex: 5+4 = 4+5

Name this property …

46 + 21 = 21 + 46 Commutative Property


69 + 0 = 69Identity Property


35 + (42 +56) = (35 + 42) + 56

Associative Property


93 + 28 = 28 + 93Commutative Property


16 + (24 + 18) = (16 + 24) + 18Associative Property


99 + 0 = 99 Identity Property

GOAL: By the end of this lesson, we will ALL be able to write and evaluate addition and subtraction expressions

• Expression – has numbers and operation signs but does not have an equal sign

Example: (15 + 5) – 7

• Variable – a letter or symbol that represents an unknown number

Example: 18 – n

# 1 Rule!!!!!!!!

Remember to ALWAYS do parentheses first!

Find the value of each expression …


14 + (7 +3) 14 + (10) 14 + 10 = 24



17 – (6-5) 17 – (1) 17 - 1 = 16



(9-8) + 4 (1) + 4 1 + 4 = 5



(6 + 9) - 2 (15) - 2 15 - 2 = 13



__ - 18 if __ = 30 ___ = 3030 – 18 = 12



8 - __ if __ = 6__ = 68 – 6 = 2



20 – (5 – c) if c = 3C = 320 – (5-3)20 – (2)20 – 2 = 18

Write an expression to match the words …

Remember you might need to add parentheses!

Tom caught 15 fish. He caught 7 more. He threw 2 back.

(15 + 7) - 2

Which number makes the equation __ + 5 = 14 true?

A. 8B. 9

C. 10

B. 9

Did we meet our goal today?

GOAL: By the end of this lesson, we will ALL be able to write and evaluate

addition and subtraction expressions

Any questions?

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Write and Evaluate Expressions GOAL: By the end of this lesson, we will ALL be able to write and evaluate addition and subtraction expressions