Brunswick Third Grade Team
Math Unit # 2
Dear Parents,
Students will now be working on computation in math class. We will
continue to work very hard in class to master these skills. This packet will
provide details of the concepts we will be teaching during our second math
unit. Please know that this is only a resource to keep you informed on the
concepts we are learning in class. Please remember that these concepts will
be introduced over time. This is designed to allow parents the opportunity to
practice and reinforce these skills at home. Thank you for your help this
year!
Properties of Addition:
Students will be learning about the Commutative, Identity, and Associative
Properties of Addition. They will be able to understand what each property
means, give examples of each property, be able to identify and distinguish
between the three.
Commutative Property of Addition:
- The Commutative Property states that you can add two numbers
together in any order and still get the same answer.
- This is similar to turn around facts the students learned last year in
second grade.
Examples:
4 + 5 = 9 and 5 + 4 = 9
10 + 20 = 30 and 20 + 10 = 30
Identity Property of Addition:
- Any number added to zero is always going to stay the same. Adding
zero to a number does not change the value.
Example:
5+0=5
1,000 + 0 = 1,000
Associative Property of Addition:
- When adding three or more numbers the answer is going to be the
same, regardless of the order you add the numbers.
Example:
(1 + 2) + 3 = 6 and 1 + (2 + 3) = 6
- Students will also learn to solve operations inside of parenthesis
first, by following the order of operations.
Adding Three or More Numbers:
Students will be able to find the sum of three or more numbers added
together. They will use the Associative Property of Addition to find
strategies to make this process easier.
Practice Examples:
3 + 9 + 7 = 19
8 + 4 + 2 = 14
7 + 8 + 9 = 24
- Encourage students to look for numbers that may add up to 5 or 10.
If you look at the first example the number sentence is much easier
to solve if the student first adds 3 to 7 and then adds 9. The same
can be said about the second example. Adding 8 and 2 first will
equal 10 and then 10 + 4 equals 14.
- Encourage students to check their work by adding the numbers in
at least two combinations. For example 7 + 8 is 15, plus 9 more is
24. 9 added to 8 is 17, plus 7 more is 24. Having the students
check their work by using to Associative Property of Addition not
only increases the success rate for computation, but also reinforces
the practical uses of the Associative Property of Addition.
- Students will also be adding three or more two digit numbers.
Practice Examples:
42 + 31 + 54 =
24 + 34 + 41 =
- Students will not be regrouping while adding at this time. That
will come in unit three.
Addition Patterns:
Students will recognize patterns that exist when adding numbers. These
patterns will help students add certain numbers mentally at a quickened
pace.
Practice Examples:
3+5=8
30 + 50 = 80
300 + 500 = 800
- Students will need to be able to identify the value of the missing
numbers that may come up in a number sentence.
- Students will also learn about variables, and a letter in a number
sentence represents a missing number.
Practice Examples:
2+4=6
20 + 40 = 60
200 + x = 600 what does x equal?
Fact Families:
Students will understand the relationship between addition and subtraction in
a number sentence. A fact family is a group of three numbers that can be
written into four number sentences, two addition and two subtraction.
Practice Example:
- Using the numbers 3, 8, and 11 write four number sentences to
complete the fact family. Two will be addition, and two will be
subtraction.
3 + 8 = 11
8 + 3 = 11
11 – 8 = 3
11 – 3 = 8
Students will also need to identify related addition or subtraction facts for a
given number sentence.
Practice Example:
12 – 5 = 7
Write an addition fact that is related to this subtraction fact.
Students can write 7 + 5 = 12 or 5 + 7 = 12
Finding the Missing Number:
Students will begin to understand the basic concepts of algebraic equations.
They will understand that a letter in a number sentence is a variable to solve
for.
Practice Example:
8 + x = 10
10 – x = 5
x = _____
( x = 2)
x = _____
( x = 5)
6+2=2+x
x = _____ ( x = 6)
- Students will also identify the missing number to complete fact
families.
3+x=8
x+3=8
8–3=x
8–x=3
x = ______ ( x = 5)
Writing a Number Sentence:
Students will learn how to identify and write number sentences to show their
work after solving a math problem. Students will use number sentences to
solve word problems
Practice Example:
Bill collects stamps. He has 7 blue stamps and 5 red stamps. How
many stamps does he have?
- Students will write 5 + 7 + 12 instead of just 12. This way
students are able to get into the habit of showing their work when
solving equations.
Solving Word Problems:
Students will be using subtraction and addition to solve word problems.
They must determine what operation they will need to use to solve the
problem.
- Students will look for key words.
- Addition: add, sum, total, plus, in all, altogether, how many
- Subtraction: minus, subtract, difference, how many more
Creating Word Problems:
Students will be given a number sentence and will need to come up with a
word problem for said number sentence.
Practice Example:
3+5=8
- Students would write something similar to this:
Three frogs jumped off a log and landed in the pond.
Then five more frogs jumped off the log and landed in the pond.
How many frogs jumped off the log and landed in the pond?
Addition:
Students will continue to practice addition problems in math. They will
range from basic single digit facts to adding numbers up to the thousands
place value. Again we are not studying regrouping yet that will come in
Unit 3.
Practice Examples:
4, 321
+ 3, 456
7 + 8 = ______
23 + 54 = _______
Subtraction:
Students will continue to practice subtraction problems in math. They will
range from basic single digit facts to subtracting numbers up to the
thousands place value. Again we are not studying regrouping yet that will
come in Unit 3.
Practice Examples:
6,478
- 4,154
9 – 6 = _____
75 – 24 = ______
Chapter 2 Concept Checklist
The following is a checklist you may want to use to track your child’s
progress. Again this is an optional form for you, designed to keep you
informed of your child’s progress. It does not need to be completed but is
simply a resource available to you if you wish to utilize it.
Concept
Commutative Property
Identity Property
Associative Property
Adding 3 or More
Numbers
Addition Patterns
Fact Families
Find the Missing
Number (x)
Writing a Number
Sentence
Solving Word
Problems
Creating a Word
Problem
Addition
Subtraction
Mastered