Adding and subtracting decimals

Adding and subtracting decimals is a similar process to the one used to add and subtract whole numbers. Understanding place value is most important to the process.

Adding decimals

If you were adding whole numbers, you might set out the calculation 453 + 136 in this way with the place values of each number lined up.

Decimal place value

	H	T	O
	4	5	3
+	1	3	6
=	5	8	9

When the calculation involves adding the decimal numbers 453.741 and 136.157, you set out the working in a similar way, making sure that the place value parts and the decimal points are lined up.

Decimal place value

	H	T	O	.	tenths	hundredths	thousandths
	4	5	3	.	7	4	1
+	1	3	6	.	1	5	7
=	5	8	9	.	8	9	8