(KS2, Year 4)

Addition is the bringing together of two or more numbers (or objects) to make a total or sum. For example, 2 apples plus 3 apples makes 5 apples: adding_apples In numbers:2_plus_3_equals_5Addition is denoted by the plus sign, +.

How to Add

The method used to add numbers will differ depending on the difficulty of the sum. Adding short numbers together is easier than adding long numbers together.

How to Add Short Numbers Together

It is easy to add short numbers. Children learn to count fingers or objects for small sums. A number line can be used to add. For example, 2 + 3 can be performed on a number line:2_plus_3_equals_5_number_line

How to Add Long Numbers Together

It is more difficult to add numbers greater than 10 together. For example: 225_plus_63 This sum is made easier when we notice numbers are made of hundreds, tens and units (i.e. the place value of the digits in the number). 225_hundreds_tens_units This allows the numbers to be broken down:225_and_63_htu_partsEach part - the hundreds (in blue), the tens (in yellow) and the units (in red) - can then be added to each other:225_plus_63_htu_parts_addThese 3 parts can then be added to give the answer: 225_plus_63_htu_parts_add_answer The solution to 225 + 63 is 288. This method of breaking numbers down into hundreds, tens and units is the basis for long addition, which offers a more systematic way of doing addition.

How to Do Long Addition

Long addition involves writing each number in columns and adding a column at a time. As each column represents the hundreds, tens and units of the numbers, long addition implicitly breaks the addition down into adding the hundreds, tens and units, but without you having to think about it:


Write the numbers you wish to add, one underneath the other. Ensure they are aligned with each other so the units of one number is directly underneath the units of the other: 225_plus_63_htu_long_addition


Add up the numbers in the units column.
5 + 3 = 8
225 plus 63 htu long addition step 2


Add up the numbers in the tens column.
2 + 6 = 8
225 plus 63 htu long addition step 3


Add up the numbers in the hundreds column.
2 + 0 = 2
225 plus 63 htu long addition step 4
The solution to 225 + 63 is 288.

Lesson Slides

The slider below shows another example of how to do long addition:
long addition

Parts of Addition

sum explained
  • The numbers you add together are addends.

  • The result of adding the numbers is the sum (or total).

Order of Addition

The order in which numbers are added does not matter. For example: 2_plus_3_equals_5_mini If the 2 and 3 are swapped around, the sum is the same: 3_plus_2_equals_5_mini This is the commutative property of addition - changing the order does not change the result. Line Up the Columns! When doing long addition, ensure you align the numbers in the correct columns, so the units are all in the units column etc. For example, the following would be incorrect: long_addition_misaligned The units of 63 (3) is underneath the hundreds of 225 (2). Adding the columns would give: long_addition_misaligned_incorrect_answer This is incorrect.


When adding numbers in a column, sometimes the sum may be 10 or more: long_addition_carry_1 Adding the units above gives 12. To do long addition correctly,
  • Write the 2 in 12 immediately below the numbers just added:
    long addition carry 2
  • Write the 1 in 12 underneath the column to the left (this is carrying the 1):
    long addition carry 3
  • When adding the left column, be sure to add the 1 along with the other numbers (2 and 6):
    long addition carry 4
author logo

This page was written by Stephen Clarke.

You might also like...

Help Us Improve Mathematics Monster

  • Do you disagree with something on this page?
  • Did you spot a typo?
Please tell us using this form.

Find Us Quicker!

  • When using a search engine (e.g., Google, Bing), you will find Mathematics Monster quicker if you add #mm to your search term.

Share This Page

share icon

If you like Mathematics Monster (or this page in particular), please link to it or share it with others.

If you do, please tell us. It helps us a lot!

Create a QR Code

create QR code

Use our handy widget to create a QR code for this page...or any page.