Decimals
NZ Level 5
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Subtract single or double digit numbers with at least 1 number with hundredths place
Lesson

Regrouping with whole numbers

When we subtract whole numbers, place value is important and we might solve a problem like

 $643-331=312$643331=312 

To solve this example, we may need to regroup before we subtract. You can look at this topic on adding and subtracting 3 digit numbers to remind you how to do this.  

 

Working with decimals

The process of subtracting numbers with decimal values is just the same, although there are now values in the columns after the decimal point. The first three are 'Tenths,' 'Hundredths' and 'Thousandths.' Watch this video now to see how we solve a subtraction question with decimal values. 

In the second video, you can see an example of subtracting two numbers that have three decimal places, but this time we need to regroup, or rename, some decimals. We use the same process that we use for whole numbers, so your prior knowledge, as well as the first video, will help here.  

 

Subtracting decimals without a place value table

Finally, in our third video, we work through an example without the place value table! Hopefully you have seen how it helps, and now feel confident to try this yourself. It's the same process, but we need to be careful with how we write our answers, so that our numbers line up in the correct places.  

We will also look at how to regroup from decimals to whole numbers. You'll soon see it's the same process we always use, we just have to keep moving left. So, when we can't subtract our tenths, what do we call on? That's right, the units!

Remember!

When working with decimals, we follow the same process as we use with whole numbers.  It's only the value of the numbers that will change.

 

Examples

Question 1

Find $9.279-9.214$9.2799.214, writing your answer in decimal form.

QUESTION 2

Find $96.491-71.3$96.49171.3, writing your answer in decimal form.

QUESTION 3

Find $0.549-0.367$0.5490.367, writing your answer in decimal form.

Outcomes

NA5-3

Understand operations on fractions, decimals, percentages, and integers

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