3rd grade math concepts

Find here many important 3rd grade math concepts taught in 3rd grade. Teachers, parents, and math tutors can also use them as a guideline to illustrate a math lesson or to teach important skills that kids are supposed to know in 3rd grade math.

A segment is a portion of a line and it has 2 endpoints.


Identity property of addition
Any number plus zero is equal to the number

5 + 0 = 5
2 + 0 = 2

Parallel lines
Parallel lines never meet no matter how long you extend the lines

Parallel lines

1 inch
1 inch is about the size of a quarter.
1 foot = 12 inches

1 inch

12  ÷  3
Share 12 soccer balls with 3 friends equally.
Just make 3 equal groups with 12.
The number of balls in each group is the answer.

12 divided by 3

Gram/ kilogram
1 gram is about the mass of 1 paperclip.
1000 grams  = 1 kg
About 1000 paperclips will be equivalent to 1 kg.
1 large book could also have a mass of 1 kg.

mass of a paperclip is about 1 gram

Expanded form
The expanded form shows the place value of each digit. 

478 = 400  + 70 + 8

The number that is used to divide. For example if 6 is used to divide 48, 6 is the divisor.


A factor is a number that is multiplied by one or more numbers. For example, in 3 × 5, 5 is a factor since 5 is multiplied by 3. By the same token, 3 is also a factor since it is multiplied by 5.


The amount of space inside a 2-dimensional object.


Word form of numbers

For example, the word form of 24652 is  "twenty four thousand, six hundred fifty-two"

Addition algorithm

Addition algorithm

Commutative property of multiplication
The order in which two numbers are multiplied in a multiplication problem does not matter.
6 × 2 = 2 × 6

Commutative property of multiplication

Identity property of multiplication
Any number multiplied by one is equal to the number.

5 × 1 = 5
2 × 1 = 2

Commutative property of addition.
The order in which two numbers are added in an addition problem does not matter.

1  + 2   =   2 + 1 
       =     3

Illustration of the commutative property

More important 3rd grade math concepts

The perimeter is the distance around a closed figure.
Perimeter = 2 cm + 2 cm + 4 cm + 3 cm
                  = 4 cm + 4 cm + 3 cm
                  = 8 cm + 3 cm
                  = 11 cm

Perimeter of a trapezoid

Fact family
A group of 3 numbers that are related in a special way. Doing math with 2 numbers always give the last number.

Fact family

What is the next shape? The next shape is the green heart.


A figure that has 5 sides is called a pentagon.


The number that will be divided is the dividend. For example, if 48 is divided by 6, 48 is the dividend.


A point is an exact location on a piece of paper represented with a single dot 


Standard form
The standard form is the base 10 numeration system or the usual way of writing numbers.


Unit fraction
A fraction whose numerator is equal to 1. The denominator can be equal to any number.

Unit fractions

Round a number

28 is closer to 30, so the nearest 10 is 30.
28 rounded to the nearest 10 is 30.

23 is closer to 20, so the nearest 10 is 20.
23 rounded to the nearest 10 is 20

Nearest 10 for 28

The answer to a multiplication problem. For example, the product of 3 times 5 is 15.


Divide a rectangle into 4 equal smaller rectangles.
Take 1 rectangle out of 4. The fraction is 1/4.

1 out of 4

The answer to a division problem. For example, when you divide 48 by 6, the answer is 8. So 8 is the quotient.


Find the value of an expression.

Evaluate 2n + 5 when n = 3

2 × 3 + 5 =  6 + 5 = 11     

Equivalent fractions.
Equivalent fractions are fractions that have the same value, but have different numerators and denominators.

Equivalent fractions

Order of operations
The proper way to do the math or rule to follow when a math problem has a combination of different operators (+, -, 
×, etc.). 

Order of operations

Three fourths
The circle has 4 parts. 3 parts of the circle are shaded.
The numerator is 3 and the denominator is 4.

Three fourths

Algorithm for adding 28 and 14

Algorithm for adding  28 and 14

Things to keep in mind about the 3th grade math concepts on this page

1. Make sure that students understand most of the 3rd grade math concepts above taught in 3th grade math. If you would like to measure their understanding of these math skills taught in 3th grade math, please check this 3rd grade math test.

2. These 3th grade math concepts are in line with 3th grade math common core state standards.

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