What is Mental Addition

Tiffany Maths dress

Tiffany likes maths and loves to learn how to calculate. She likes to wear her numbers dress when she is learning maths.

Tiffany has been learning about mental addition.

Did you know?

Mental addition means adding two or more numbers in your head (without using pen and paper).

Being able to add numbers in your head is a good skill to learn and will save time with calculations.

The more you practice mental addition the easier it will become.

 

Using number bonds to help with mental addition

Learning as many number bonds as possible will definitely help with mental maths.

If you know your number bonds to ten then you will know immediately that

8 + 2 =10

If you know your number bonds to twenty then you will know immediately that

15 + 5 = 20

If you know your number bonds to one hundred then you will know immediately that

30 + 70 = 100

You can learn number bonds to any number – 10, 20, 30, 40, 100, 1,000 etc

 

Using mental addition to add lots of single digit numbers

If you are asked to add together 2, 6, 8, 5, 1, and 9, you can add them together in stages

2 + 6 = 8

8 + 8= 16

16 + 5 = 21

21 + 1 = 22

22 + 9 = 31

 

Another way to add 2, 6, 8, 5, 1, and 9 in your head would be to use number bonds

2 + 8 = 10

9 + 1 = 10

6 + 5 = 11

10 + 10 + 11 = 31

Using mental addition to add large numbers

Adding larger numbers in your head is much easier if you break the numbers up. This is called chunking or partitioning.

Here is an example of how this works:

45 + 36 = ?

Using partitioning, 45 is the same as 40 + 5 and 36 is the same as 30 + 6

40 + 30 = 70 and 5 + 6 = 11 add together the two answers 70 + 11 = 81

so

45 + 36 = 81

 

This method works with bigger numbers

226 + 133 = ?

Using partitioning 226 is the same as 200 + 20 + 6 and 133 is the same as 100 + 30 + 3

200 + 100 = 300, 20 + 30 = 50 and 6 + 3 = 9

Add together the answers – 300 + 50 + 9 = 359

226 + 133 = 359

 

Tiffany has enjoyed learning about mental addition and now knows how to add up numbers in her head using number bonds and partitioning. She summed up her learning with the following keywords:

addition, calculation, chunking, counting, digit, mental, number bonds, partitioning