Find here many important second grade math concepts taught in second 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 second grade math.

**Doubles**In doubles, both addends are the same.

1 + 1 = 2 2 + 2 = 4

3 + 3 = 6 4 + 4 = 8

5 + 5 = 10 6 + 6 = 12

**How to decompose a number**To decompose a number is to break down the number into its two or more parts.

**Equal groups**Equal groups are groups that have the same number of items.

**Estimate:**No need to get an exact answer. For example, estimate the numbers of hearts you see below. No need to count!

Possible answer: 35, 40 or 30

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What is the meaning of **a.m.** ?

12:00 a.m. : midnight; sleeping time

7:30 a.m. : half past 7; wake up time

10:15 a.m.: a quarter after 10; doing work in class.

**Example of angle.**When two lines meet at a common point, they make an angle.

**Bar graph**A graph that uses rectangles to compare data. Saturday got 15 votes.

**Array**The array you see below is made with triangles. The array has 4 rows and 5 columns.

4 × 5 = 20 triangles.

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What is the **associative property**?

No matter how you group the three numbers below before adding, you will still get the same answer.

8 + 5 + 2 = (8 + 5) + 2

= 8 + (5 + 2)

**Even number**

There are 10 balls and 10 is an even number. An even number has 2 equal parts. 10 has 2 equal parts. Each part is equal to 5.

**Count back**

7 - 4

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**1 Dollar**1 dollar is a currency used in the USA that is equal to 100 cents.

1 dollar = 100 cents

What is a **number line**?

**Word form of number**

The word form of 345 is "three hundred, forty-five"

The word form of 268 is "two hundred sixty-eight"

**Odd number**

There are 9 balls and 9 is an odd number. An odd number does not have 2 equal parts. One part is is 5 and the other is 4.

**Quadrilaterals**Quadrilaterals are closed figures with 4 straight sides. For example, squares, rectangles, and parallelograms are quadrilaterals.

**Standard form**

A familiar way of writing numbers using digits.

432

**Tens**

1 long is a physical representation of 10.

**Vertex**

A point where 2 or more sides of shape meet. The vertex of the cube you see below is shown with a small white circle.

The vertex of the triangle you see below is shown with a small red circle.

**Fourths**

The parts that we get when something is divided into 4 equal parts.

What is the meaning of **p.m.**?

12:00 p.m. : noon ; lunch time

3:30 p.m. : half past 3 ; nap time

6:45 p.m.: a quarter to 7 ; dinner time

**Line plot**A line plot shows data on a number line using x or some other marks to show how many times a number appears.

The number 6 appears 3 times.

The number 4 appears once.

**What is an equation**?

An equation shows that two things are equal. For example the equation 4 + 8 = 12 is saying that 4 + 8 is equal to 12. An equal sign must be there to call something an equation!

4 + 8 = 12

14 = 6 + 8

**Compare numbers**

4 is smaller than 8 or 4 < 8

8 is bigger than 4 or 8 > 4

**Centimeter ruler**

**Centimeter or cm**

The width of a finger or the diameter of a wedding ring is about 1 centimeter long.

The length of a baseball bat is about 1 meter.

1 meter = 100 centimeters

**Count on**5 + 3

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**USA money**

One dollar + 1 quarter + 1 dime + 1 nickel + 1 penny = 1 dollars and 41 cents.

**Fractions**

**Regroup**Regroup 15 ones as 1 ten and 5 ones

**Pictograph**Key of a pictograph. Each face = 1 player.

2 people loves soccer.

**Flat**

10 tens or 10 long = 1 hundred or 1 flat

**Sequence**

+5 +5 +5

3 8 13 18

**Place value**The value of a digit based on where the digit is located. The place value of 4 in 546 is 40.

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

**2.** These second grade math concepts are in line with second grade math common core state standards.