2. Addition and subtraction

Lesson

Do you remember how to solve addition problems using an algorithm?

Find the value of 41+56.

Worked Solution

Idea summary

You might notice that sometimes the standard algorithm is called the 'vertical algorithm'. Let's think about why. When we use the standard algorithm, we line our numbers up in 'vertical' place value columns.

Let's see how place value models (also called Base 10 models) can help us with adding numbers together.

We can also use a number line to help with addition, so let's see how we solve the same problem, 321 + 243, using a number line this time.

Use the number line, to help you find the value of 19 + 343.

Worked Solution

Idea summary

When we add on a number line, we move to the right. It is usually easiest to start with the larger number and add the smaller number.

This time we add some 4-digit numbers, using place value columns.

Find the value of 4400 + 403.

Worked Solution

Idea summary

There are different ways to solve addition problems, and you can use them to add numbers of different sizes. It doesn't matter if your number has 3 digits, 4 digits, or even more.

uses mental and written strategies for addition and subtraction involving two-, three-, four and five-digit numbers