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The aim of this guide is to show how to add decimals with a different number of decimal places. We will focus on the formal written method.

Let's look at some examples.

What is 4.5 + 3.26?

Set out the calculation, making sure each digit is lined up in the correct column based on its place value and that the decimal points are directly underneath one another. We need to be careful here as the numbers have a different number of places.

You can write 4.5 as 4.50. This does not change the value of the number, but it may help when setting out and completing the calculation.

Starting with the column on the right with the least place value, i.e. with hundredths in this example, we say:
**6 hundredths plus 0 hundredths is 6 hundredths,
5 tenths plus 2 tenths is 7 tenths and
4 ones plus 3 ones is 7 ones. **

What is 47.48 + 6.759?

The first decimal has two decimal places and the second decimal has three decimal places.

Set out the calculation, making sure each digit is in the correct column based on its place value and that the decimal points are directly underneath one another.

You can write 7.48 as 7.480.

Starting with the thousandths column, 0 thousandths plus 9 thousandths is 9 thousandths.

Moving to the hundredths column, 8 hundredths plus 5 hundredths is 13 hundredths, which is the same as 1 tenth and 3 hundredths.

Moving to the tenths column, 4 tenths plus 7 tenths plus the 1 ‘extra’ tenth is 12 tenths, which is the same as 1 one and 2 tenths.

Moving to the ones column, 7 ones plus 6 ones plus the 1 ‘extra’ one is 14 ones, which is the same as 1 ten and 4 ones.

What is 6.1 + 2.685 + 7.49?

Set out the calculation, making sure each digit is in the correct column based on its place value and that the decimal points are directly underneath one another.

You can write 6.1 as 6.100 and 7.49 as 7.490.

Starting with the thousandths column, 0 thousandths plus 5 thousandths plus 0 thousandths is 5 thousandths.

Moving to the hundredths column, 0 hundredths plus 8 hundredths plus 9 hundredths is 17 hundredths, which is the same as 1 tenth and 7 hundredths.

Moving to the tenths column, 1 tenth plus 6 tenths plus 4 tenths plus the 1 ‘extra’ tenth is 12 tenths, which is the same as 1 one and 2 tenths.

Moving to the ones column, 6 ones plus 2 ones plus 7 ones plus the 1 ‘extra’ one is 16 ones, which is the same as 1 ten and 6 ones.

What is 7.85 + 6 + 9.4?

Set out the calculation carefully. Think about the place value of each digit and ensure that the decimal points are directly underneath one another.

Remember that 6 is – of course – 6 ones and can be written as 6.0. You can write 6.0 as 6.00 and 9.4 as 9.40.

Starting with the hundredths column, 5 hundredths plus 0 hundredths plus 0 hundredths is 5 hundredths.

Moving to the tenths column, 8 tenths plus 0 tenths plus 4 tenths is 12 tenths, which is the same as 1 one and 2 tenths.

Moving to the ones column, 7 ones plus 6 ones plus 9 ones plus the ‘extra’ one is 23 ones, which is the same as 2 tens and 3 ones.