Variables and Unknowns, Number Sentences, Expressions,
Polynomials
IS2-6
Instructional Support Strategies/Resources
Variables and Unknowns
2.2.2
Model, explain, and identify missing operations and missing numbers
in open sentences involving number facts in addition and subtraction.
Number Sentences, Expressions, and Polynomials
2.2.3
Complete number sentences with the appropriate words and
symbols (+,-,=). I
2.2.3
Represent mathematical situations using numbers, symbols, and
words.
Content Connection
Variables are symbols that take the place of numbers or ranges of numbers. Their
meaning changes depending on whether they are being used to represent the
quantity that varies or changes or if they represent the specific unknown value. It
is important for teachers to have an accurate understanding of variable and
equations so that we can help students construct appropriate ideas. By the end of
grade 2, students should be able to demonstrate this understanding by modeling,
explaining, and identifying missing operations or numbers in open sentences.
Instructional Strategies
1. As previously suggested, second grade students can play a game in pairs that
uses color tiles or any type of counter. Start with a maximum of 18 tiles, one
student covers up a certain amount, and then asks the other child what is the
missing addend.
2. Give half of your class number cards and the other half symbol cards. Through
trial and error, kids would pair up with another to make number sentences and
expressions.
Working copy
2007/2008
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3. Names for Numbers
Challenge your students to find different ways to express a specific number.
For example, ask how many names they can find for the number 8, using only
numbers less than 10 and at least three operations.
4. Tilt or Balance
Draw a simple two-pan balance. In each pan, write a numeric expression and
ask which pan will go down or whether they will balance. Challenge students to
write expressions for each side of the scale to make it balance.
Connection to Children’s Literature
Two of Everything by Lily Toy Hong
Anno’s Math Games II by Mitsumasa Anno
The McSquares by Marilyn Burns
Working copy
2007/2008
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