Decimals
NZ Level 5
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Multiply numbers with tenths by single digit numbers
Lesson

Multiplying decimals

Multiplying decimals by single digit numbers is similar to multiplying whole numbers by single digit numbers.  We know there are some different ways to solve multiplication problems, so using these approaches with our decimals is useful also.

In our first video, we look at what it means to multiply a decimal by imagining what it would look like. We also look at how to break up our number to solve a decimal multiplication. 

Remember!

We can solve a decimal multiplication by:

  • breaking up the number,
  • solving end multiplication separately, then
  • adding all the parts together

Strategies for multiplying

In the second video, we look at some of the strategies we use in multiplication to help us multiply decimals.  Repeated addition, partitioning and thinking of place value are all useful ways to break down decimal problems in to smaller problems.  

Multiplying vertically

In our final video, we look at using a vertical algorithm, to solve $14.7\times9$14.7×9, making sure we place our decimal point correctly at the end. This means we work down our page to multiply.

Remember!

When we multiply decimal numbers, we do the same as if we are multiplying whole numbers, it's just that the value of some of our digits is lower.

Worked examples

Question 1

Find $0.3\times5$0.3×5, giving your answer as a decimal.

Question 2

Find $6.2\times9$6.2×9, giving your answer as a decimal.

Question 3

Find $9\times32.9$9×32.9, giving your answer as a decimal.

Outcomes

NA5-3

Understand operations on fractions, decimals, percentages, and integers

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