Operations: Multiplying Decimals

SYLLABUS DOT POINTS

• Determine the effect of multiplying or dividing by a number with magnitude less than one
• Multiply and divide decimals by powers of 10
• Multiply and divide decimals using written methods, limiting operators to two digits
• Multiply and divide decimals using a calculator

WORKING MATHEMATICALLY INDICATORS

Students will:

• Use appropriate methods to multiply decimals by numbers with magnitudes less than one. (Problem Solving, Understanding)
• Identify the process for multiplying decimals by powers of 10. (Understanding)
• Compare initial estimates with answers obtained by written methods and check by using a calculator. (Problem Solving)

LEARNING GOALS

By the end of this lesson students will be able to:

• Demonstrate what happens when a number is multiplied by a magnitude less than one.
• Multiply decimals by powers of 10. (With close notice of the positioning of the decimal point itself).
• Be able to multiple decimals together using both written and calculator methods.

MATERIALS REQUIRED

• Laptops
• Whiteboard markers and rubber

The main focus of this lesson would be to continue on with decimal multiplication (I decided to split it into two lessons because I thought that one lesson would have been to content heavy for the students). In this lesson students would be introduced to more challenging decimal multiplication. It might also be valuable for the students if the beginning part of the lesson involved a quick recap of what was introduced last lesson.

Students would learn to multiply a decimal by another decimal for the first time. Firstly using written methods and then through using a calculator. The importance and relevance would be emphasised by drawing from real life situations that involve the multiplication of decimals. A possible example could be through giving an example with area and how sometimes the length of a rectangle could be 4.2 metres long and 3.75 wide and how you have to multiply those numbers together to get the answer. After this lesson students should then be ready to move onto dividing decimals.

INTRODUCTION (15 MINUTES)

Initially, the homework from last lesson will be looked at. If there were any particular questions students had any issues with the teacher would address them on the board. The teacher would also go through the solutions from the assessment for learning quiz. The teacher would then explain what the focus of this lesson would be. It would be explained to students that this lesson will look at multiplying two decimals with each other. The teacher would first hand out a sheet to each student that looks at the area model for decimal multiplication. (It is the 4th Resource down). The teacher would then go through the example, 0.8 multiplied by 0.7, and show that this is in fact 0.56. This could prove to be a good way to show students that the multiplication of decimals is not as daunting as it might seem.

The teacher would then show students an example which involves decimal numbers with more decimal places. Questions the teacher could ask could be, ‘do we have to do the same as what we do with addition and line up the decimal points?’ and 'Is it alright to just make one of these a decimals a whole number or do we have to keep going?' Once the example has been completed, with the teacher stressing that both need to be made into whole numbers, the teacher could then explain to students that you could also use your calculator to complete the question instantly, depending on the question.

BODY (30 MINUTES)

(15 MINUTES)

Now the body of the lesson would occur. Students would first be instructed to split into pairs and play the online basketball game that looks at multiplying decimals with each other. (It is the 1^st resource down). Students would be encouraged to pause every time a new question appears so that they can write down the correct working required to complete the examples (Communicating, Fluency). Once students have had approximately 15 minutes to do this the teacher would stop the class and ask students if they came across any particularly hard questions. The teacher would complete these on the board.

(15 MINUTES)

Next, the teacher would instruct students to form bigger groups by getting two pairs to merge with each other. Students would then be instructed to work on Microsoft Excel and go through a number of multiplying and dividing examples (formulas, steps and questions will be written on the board) (Communicating). Once students have moved through the allocated questions they would then be encouraged to experiment with the program and put in numbers of their own choosing. When this is occurring the teacher would circulate around the room. They could ask questions like, ‘how would you get this answer without excel?’

ASSESSMENT FOR LEARNING AND CONCLUSION (15 MINUTES)

(10 MINUTES)

The teacher would then organise a small quiz at the end of class with the online program Kahoot to consolidate what was learnt today (AFL). Here students would be required to do this individually. Once the quiz is completed the teacher would explain the solutions to students.

(5 MINUTES)

Once the quiz is over the teacher would re-emphasise the key points from today. For example, the teacher could say, 'Multiplying decimals seems complicated at first but isn't really. The main thing I want you to remember is that when you are multiplying decimals all you do is you move the decimal places so that you make both our decimals whole numbers!" For homework the teacher could then allocate some carefully selected textbook exercises that look to consolidate what was learnt today.

LESSON EVALUATION QUESTIONS

Did students enjoy the use of virtual manipulatives?

Was the basketball game a good substitute for textbook questions or worksheets?

Did students like the use of Excel or were they disinterested?