Add two 3-digit numbers

Learning focus

In this lesson, you will learn how to add two three-digit numbers together.

This lesson includes:

  • one quiz
  • one learning summary
  • one video
  • two practise activities

Quiz

Check your knowledge of adding two 3-digit numbers together in this quiz. Get your pen and paper handy and try using the column method.

Learn

First, let’s find out a bit about the method for adding numbers together using number columns. Watch this short animation featuring a hive of helpful bees from KS2 Maths.

Checklist

There are a few things you should always do when adding large numbers together:

  • When writing down sums, separate the numbers into ones, tens and hundreds. List the numbers in a column and always start adding with the ones first.
  • Estimate first and check afterwards - it's a good idea to estimate a rough answer first and then check your actual answer.
  • Order doesn't matter - remember that 345 + 129 is the same as 129 + 345.
  • Key words - look out for these words in problems: total, sum, altogether, more. They all indicate an addition calculation.

Column addition

Numbers can be added together using the column method which involves writing one number underneath the other.

Example 1

What is 343 + 315?

Start from the ones column: 3 + 5 = 8

Start from the ones column: 3 + 5 = 8.

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Example 2

What is 343 + 329?

If the two numbers in a place value column add up to a number greater than 9, you must carry a digit.

Start from the ones column: 3 + 9 = 12, place a 2 in the ones column and carry 10 to the tens column by placing a 1

Start from the ones column: 3 + 9 = 12. Write a 2 in the ones column and carry 10 to the tens column by writing a 1 below.

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Example 3

One apple tree has 178 apples. Another has 253 apples. How many apples are there altogether?

You can use the column method to solve this problem.

Start with the ones column. 8 + 3 = 11. 11 can be partitioned in to 1 ten and 1 one. The 1 one stays in the ones column while the ten gets carried over.

Start with the ones column. 8 + 3 = 11. 11 can be partitioned into 1 ten and 1 one. The 1 one stays in the ones column while the ten gets carried over.

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Practise

Activity 1

Hive maths

Click on the image below to see if you can add the numbers correctly.

Activity 2

On a piece of paper, and using the column method, try to work out the following:

  1. 258 + 351

  2. 541 + 639

  3. 745 + 362

Play

Play Guardians: Defenders of Mathematica to learn more and sharpen your skills on this topic.

Guardians: Defenders of Mathematica

There's more to learn

Have a look at these other resources.

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