Videos, solutions, examples, worksheets, games and activities to help Grade 3 students learn mental addition strategies.

In these lessons, we will learn how to describe and apply mental mathematics strategies for adding two 2-digit numerals, such as:

### Adding from left to right

Add the tens and add the ones and then combine them together.

*Example:*

46 + 12 =

40 + 10 = 50

6 + 2 = 8

50 + 8 = 58

So, 46 + 12 = 58

This is also called the**partial sums algorithm**.

**How to add two-digit numbers by adding from left to right or partial sums algorithm?**

Example:

34 + 23

**Partial Sums Strategy for adding Two Digit Numbers**

Example:

46 + 36

### Addition using Compensation

Taking one addend to the nearest multiple of 10 and then compensating

*Example:*

69 + 28 =

69 is close to 70

70 + 28 = 98

69 + 28 is 1 less

So, 69 + 28 = 97

**How to add in your head using a technique called compensation?**

Examples:

How would you use compensating to solve these problems?

34 + 49

29 + 66

53 + 28

36 + 41

21 + 35

45 + 16

34 + 25

**How to use the compensation strategy to help you to solve addition problems?**

Examples:

55 + 19

120 + 61

### Addition using Doubles

Use a doubles fact you know to help find the sum.

*Example: *

32 + 30 =

30 + 30 = 60

32 + 30 is 2 more

So 32 + 30 = 62

Adding Doubles +1**Doubles and Near Doubles (Addition strategy)**

How to use Near Doubles for addition?

When adding near doubles and one is 1 more, add the two doubles and then 1 more.

When they are apart by two, here is what you need to do. Add the two doubles and then 2 more.

In these lessons, we will learn how to describe and apply mental mathematics strategies for adding two 2-digit numerals, such as:

- adding from left to right (partial sums algorithm).
- addition using compensation
- addition using doubles.

46 + 12 =

40 + 10 = 50

6 + 2 = 8

50 + 8 = 58

So, 46 + 12 = 58

This is also called the

Example:

34 + 23

Example:

46 + 36

69 + 28 =

69 is close to 70

70 + 28 = 98

69 + 28 is 1 less

So, 69 + 28 = 97

Examples:

How would you use compensating to solve these problems?

34 + 49

29 + 66

53 + 28

36 + 41

21 + 35

45 + 16

34 + 25

Examples:

55 + 19

120 + 61

32 + 30 =

30 + 30 = 60

32 + 30 is 2 more

So 32 + 30 = 62

Adding Doubles +1

How to use Near Doubles for addition?

When adding near doubles and one is 1 more, add the two doubles and then 1 more.

When they are apart by two, here is what you need to do. Add the two doubles and then 2 more.

Try the free Mathway calculator and
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