Teach How to Multiply Decimals by Decimals

Your mum sends you to the supermarket with $10 and tells you to buy 2 kilograms of beef mince and two packages of taco seasoning. She gives you a list of prices.

Did your mum give you enough money? How do you know?

To work out the answer to this question, your students may choose a range of different strategies. One strategy they could draw upon is multiplication. As there are monetary amounts involved, the students will need to know how to multiply with decimals. There are even strategies they can choose within this strategy of multiplication!

Three of the most common strategies for multiplying decimals by whole numbers and multiplying decimals by decimals are:

1. Visual Models – This model employs the use of grids or arrays to represent decimals. Each decimal is broken down into tenths and hundredths. By shading in the appropriate areas, students can visually see the multiplication process represented on a grid. This method is ideal for learners who benefit from hands-on approaches to solving mathematical problems.
2. Area Models – This model involves drawing rectangles to represent decimals and partitioning them into smaller sections based on place value. The intersection points of the partitions contain the products, making it easier to grasp the multiplication of decimals. This method is ideal for learners who benefit from a methodical, step-by-step approach to problem solving.
3. Standard Algorithm – This method is the more traditional method we often use for multiplication. Line up the decimals, multiply as you would with whole numbers, and then adjust the decimal place in the final product. This method is ideal for learners who have a strong grasp of the underlying concepts and can complete calculations quickly and accurately.

To help your students better understand these three strategies for multiplying with decimals, the expert teacher team at Teach Starter has created this 23-slide teaching presentation. The presentation explores each strategy in detail using annotated examples of each process. It also includes collaborative review activities that the class can work through together as a means of checking for understanding.

This slide deck downloads as either a Microsoft PowerPoint or in a Google Slides format. The first part of the presentation operates in Slideshow mode. The second part (the review activities) operates in Edit mode.

Differentiate This Multiplying Decimals Slideshow

If you’re looking for ways to differentiate this activity, here are some suggestions from our experienced teacher team:

• Provide Manipulatives – To help your less-confident students engage with and practise each strategy, provide manipulatives such as hundreds grids (without the numbers), area model templates and mini-whiteboards. This way, students can complete each step of each new strategy as it is being described in the slideshow.
• Be the Teacher – Allow your more-confident students to demonstrate their knowledge by taking the lead during the review activities. Have students take turns coming up to the board and walking the class through the steps required to complete the questions.

Download to Multiply a Decimal by a Decimal

Use the dropdown menu on the Download button to access your preferred version of this resource. (Note: You will be prompted to make a copy of the Google Slides presentation before accessing it.)

Project the resource onto your screen and work through the slides as a class for a paperless lesson on how to multiply decimals by decimals!

This resource was created by Kaylyn Chupp, a Teach Starter collaborator.

More Decimals Operations Resources

If you love the look of this decimals resource, then we have good news for you! We have plenty more resources to complement your lessons on multiplying decimals! Click below to browse more teacher-created, curriculum-aligned resources!

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