Adding 3-digit and 1-digit numbers together

Addition involves finding the total of two or more numbers or amounts.

There are different things you can use to help you add. You can use number lines, place value charts and place value counters.

Knowing how to partition numbers and number bonds can make addition easier. It can even help you to work out the answer in your head.

Test out your knowledge of adding 3-digit and 1-digit numbers together with this quiz, then read on to complete the page.

It's really helpful to understand hundreds, tens and ones when adding numbers together.

You can break down each number into its place values and add them separately.

Imagine you are adding 5 + 3. You might be able to work it out in your head.

The answer is 8.

Now try adding 25 + 3.

That’s two tens and 8 ones. The answer is 28.

If you already know that 5 + 3 = 8, then you also know that 25 + 3 = 28.

Now try adding 325 + 3.

This looks a bit tricker - but you can still work it out if you keep thinking about the hundreds, tens and ones.

In the number 325, there are 3 hundreds, 2 tens and 5 ones altogether.

If you add 3 more ones the answer is 328.

If you already know that 5 + 3 = 8, then you know that 325 + 3 = 328.

With practice, breaking numbers down into hundreds, tens and ones can make addition easier.

Adding using place value counters

Using place value counters can help you visualise addition by showing how numbers combine in each place value.

To add using place value counters, put the counters into columns for hundreds, tens and ones to match the values of each number you’re adding.

Let's use some place value counters to solve 438 + 5.

Adding using a number line

Sometimes when you are adding a 1-digit number to a 3-digit number you have to bridge a ten. Bridging a 10 just means crossing over to the next ten.

This happens when the ones add up to more than 9.

Knowing your number bonds to 10 can really help with this.

Let’s see how to bridge across a ten using a number line:

What is 285 + 6?

You could work out the answer by making 6 jumps of 1 along the number line.

Or you could break up the number 6 into 5 and 1.

285 + 5 gets you to 290, which is the next ten.

Now, you only need to add 1 more to reach the final answer.

So, 285 + 6 = 291.

You can use a number line to see each step clearly, breaking it down into two smaller jumps.

With practice, you might even be able to do this in your head.