Decimals

NZ Level 5

Order of operations with decimals (add/sub/mult/div)

Lesson

When we solve mathematical problems we follow some rules, to make sure we solve them correctly. Not only does this help us solve the problem, it means everyone uses the same approach. This is called the order of operations.

It's a bit like traffic lights on the road, we know that red means stop and green means go. We all follow this rule to avoid accidents and confusion!

When our number problems contain decimals, we don't need to change the way we solve them. This means there are no new rules to learn. So what order do we follow? Let's refresh our memory of the order of operations:

Order of operations

- Solve anything inside grouping symbols (e.g. brackets or parentheses).
- Do multiplication and division, going from left to right.
- Do addition and subtraction, going from left to right.

You may have already tried solving some decimal questions with three operations (addition, subtraction and division). Now, let's include multiplication as well and work through some examples.

Now let's work through some number problems that have more steps. For each problem, we look at how to solve the multiplication or division of decimals using different strategies that you can keep in your toolbox.

Careful!

Once you've solved one part of a problem, remember to always check if there are any more multiplication or division problems to solve before you solve any addition or subtraction.

Find the value of $8.9-79\div10$8.9−79÷10, giving your answer as a decimal.

Find the value of $87.2\div10+1.1$87.2÷10+1.1, giving your answer as a decimal.

Find the value of $0.6\times8-0.6\times4$0.6×8−0.6×4, giving your answer as a decimal.

Understand operations on fractions, decimals, percentages, and integers