Eligible Content M3.D.2.2.2 

Help Me To:
divide
minus
times
plus

 

 

 

Identify the missing symbol ( +, -, =, <, > ) that makes a number sentence true.

Did You Know?

You can use symbols ( +, -, =, <, > ) and numbers to write a number
sentence that describes a problem.

Look at the example below. 

Look at the matching colors to identify the parts of a number sentence.

Number sentences or equations contain numbers, operation symbols and
an equal sign or a greater than or less than symbol followed by an answer.

4  x  2  =   8

The operation symbols are   +    -    x    ÷   ( the / symbol is often used on computers)

 

Check What You Know First

Determine the missing operation symbol in the number sentence.
Write    +    -    x    ÷

13   question  7   =  6

 

  2  question  7   =   9

 

45  question  9   =   5

  5  question  6   =   30

  5  +   5  question   10

 

  8   +  4  question   10

 

  10  -  4  question   7

 

Key Vocabulary

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A plus sign ( + )  is a mathematical symbol which means to add numbers.

A minus sign ( - )  is a mathematical symbol which means to subtract numbers.

A greater than ( > )  is a mathematical symbol used to compare two numbers, with the larger number given first. 
Example:  6 > 4

A lesser than ( < )  is a mathematical symbol used to compare two numbers, with the lesser number given first. 
Example:  3 < 6

An equal sign ( = )  is a mathematical symbol which means is equal to.
Example:  3 < 6

A number sentence is a sentence that includes numbers, operation symbols, and a greater than or less than symbol or an equal sign. 
Examples:  3 + 2 = 5,    5 – 2 = 3,    4 + 1 < 6,    8 – 2 > 5

An expression is the part of a number sentence that combines numbers and operation signs, but doesn't have an equal sign or an
inequality sign.  Examples:  3 + 2,     5 - 2

An equation is a number sentence which states that two amounts are equal. Examples:  3 + 2 = 5,    5 – 2 = 3

An inequality is a mathematical sentence that compares two unequal expressions with symbols < (less than) or > (greater than).  
Examples:  4 + 1 < 6,    8 – 2 > 5

An inverse operation is an opposite operation, or operations that undo each other, such as addition and subtraction or multiplication
and division.  Examples: 3 + 2 = 5,    5 – 2 = 3,     4 x 3 = 12,     12 ÷ 3 = 4

A variable is a symbol or letter that stands for an unknown number.  Example: a + 2 = 5,   6 + 2 = n

A fact family is a set of related multiplication and division, or addition or subtraction, equations using the same numbers.
Examples:  2 x 4 = 8,     4 X 2 = 8,     8 ÷ 4 = 2,     8 ÷ 2 = 4,     1 + 5 = 6,     5 + 1 = 6,     6 – 5 = 1,     6 – 1 = 5

Learn About It Now

To solve a number sentence with a missing operation symbol, try each of the number
operations in the equation.

In this problem, since you are going from a larger number to a smaller number in the answer,
the numbers are decreasing so it would be logical to subtract.   Try the  - sign.   13 minus 7
does = 6.  The minus symbol  ( - ) is the correct answer.

13  guess   7   =   6

 

In this problem, since you are going from a smaller number to a larger number in the answer,
the numbers are increasing so it would be logical to add. Try the ( + ) sign. 2 plus 7 does = 9.
The plus symbol ( + ) is the correct answer.

2 guess   7   =   9

 

In this problem, you are going from a larger number to a smaller number in the answer.
The numbers are decreasing, but subtraction does not work in this problem. Try dividing.
Try the ( ÷ ) sign.   45 divided by 9 does = 5.  The division symbol  ( ÷ ) is the correct answer.
( the / symbol is often used on computers to show division)

 45  guess   9   =   5

 

In this problem, since you are going from a smaller number to a larger number in the answer,
the numbers are increasing at a greater amount so it would be logical to multiply. Try
the ( x ) sign.   5 times 6 does = 30. The multiplication symbol  ( x ) is the correct answer.

  5  guess   6   =   30

 

Remember, you can use your knowledge of basic math facts to find the missing symbols
in simple math problems.  That is why it is a good idea to memorize your basic math facts.

Part of memorizing the basic math facts, is being familiar with the fact families of numbers.
You can look at fact families to figure out the operation symbols in a problem. In the
following problem, the fact family would be:

4 x 5 = 20      5 x 4 = 20      20 ÷ 4 = 5      20 ÷ 5 = 4

If you know the fact family, you will know that the multiplication operation symbol (x) is the answer.

4  guess   5   =   20

 

In this problem, you must first solve the addition problem. You need to add 5 + 5 to get 10.  Then you need to compare the answer 10 to the other number 10.  When comparing two numbers, you need to decide what symbol to use:  the equal sign (=), the greater than symbol (>) or the less than symbol (<).  In this problem you would use the ( = ) symbol because 10 is equal to 10.  (5 + 5 = 10)

5  +   5  guess  10

 

In this problem, you must first solve the addition problem.  You need to add 8 + 4 to get 12.  Then you need to compare the answer 12 to the other number 10.  When comparing two numbers, you need to decide what symbol to use:  the equal sign (=), the greater than symbol (>) or the less than symbol (<).  In this problem you would use the ( >) symbol because 12 is greater than 10.  (8 + 4 > 12)

8  +   4  guess  10

 

In this problem, you must first solve the subtraction problem. You need to subtract 10 - 4 to get 6.  Then you need to compare the answer 6 to the other number 7.  When comparing two numbers, you need to decide what symbol to use:  the equal sign (=), the greater than symbol (>) or the less than symbol (<).  In this problem you would use the ( <) symbol because 6 is less than 7. (10 - 4 < 7).

10  -   4  guess  7

 

More Practice With Identifying Missing Symbols

Write the missing operation symbol that makes the number sentence true.

  11  question  3   =   14

 

  16   question  9   =   7

 

  18   question  9   =   27

 

   6   question  7   =   42

 

  25   question  5   =   5

 

  20  -  5  question  15

 

  16  -  4  question  15

 

  18  +  7  question   22

 

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Websites to Check Out For Extra Practice

Click below to practice finding a missing number and operation that makes a number
sentence true in the Function Machine.

Directions for the Function Machine Game: 
For the variable x, type a number and click on enter. 
Under the question, (Can you guess the function?), select an operation. 
Then type a number in the box that follows. 
To see if you are correct, click on check formula. 
To begin a new problem, click on the button – Set new function. 
You can also see your score by clicking on the button – Keep score.
http://www.shodor.org/interactivate/activities/fm/index.html

The following are additional websites for practicing addition and subtraction facts
and finding the missing number/answer.

Addition equations with 1 digit numbers  fill in missing numbers
http://www.aaamath.com/B/g18c_sx1.htm
 
Adding Numbers 1  - Finding the sum of numbers 1 - 10
http://www.321know.com/addk7cx1.htm 
    
Adding Numbers 2 – Finding the sum of numbers 1 -10
http://www.321know.com/addk7dx1.htm
 
Subtracting Numbers 1 - Finding the difference of numbers 1-10
http://www.321know.com/subk7hx2.htm

Subtracting Numbers 2 – Finding the difference for numbers 1- 10
http://www.321know.com/subk7ix2.htm 

Addition Facts for All to 10 + 10 - Finding the sum of addition facts to 20
http://www.321know.com/add26ax1.htm 
 
Subtraction Facts all For 0 through 10 - Finding the difference for numbers 1 - 20
http://www.321know.com/sub26bx2.htm