Mental Addition - Grade 3
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:
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
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
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.
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 compensatingExample:
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.
Check out our most popular games!
Fraction Concoction Game:
Master fractions in the lab: mix, add, and subtract beakers to create the perfect concoction!
Fact Family Game:
Complete fact families and master the link between addition & subtraction and multiplication & division.
Number Bond Garden:
Clear the board by matching number pairs that sum to ten in this garden-themed mental math puzzle.
Online Addition Subtraction Game:
Practice your addition and subtraction skills to help the penguin find its mummy.
We welcome your feedback, comments and questions about this site or page. Please submit your feedback or enquiries via our Feedback page.