# MULTIPLICATION OF THE DECIMALS

LESSON PLANNING OF MULTIPLICATION OF THE DECIMALS

Subject Mathematics

Students` Learning Outcomes

• Multiply decimals by 10, 100, 1000

Information for Teachers

• When a decimal number is multiplied by 10, the decimal point jump one place to the right, for example; 12.567 x 10 = 125.67

• When multiplying by 100, the decimal moves two places to the right, for example; 12.567 x 100 = 1256.7

• When multiplying by 1000, the decimal moves three places to the right e.g. 12.5677 x 1000 = 12567.

Step 1: count how many zeros are there in the second factor.

Step 2: in the first factor move the digit point to the right accordingly.

• Use textbook when and where required.

Material / Resources

Writing board, chalk / marker, duster, textbook

Mental mathematics

• Can you tell?

• Tell them we are appending zeros, as per 10 or according to its power?
• Announce that today we will do multiplication of decimals values by 10, 100, and 1000.
• There is a decimal point in every number!!!
• 5 are actually 5.000000…… and 84 are actually 84.0000………….
• Just like every number can also be written as a fraction 84/1, 5/1, 6/1 etc. everyone number has a decimal point too.
• Let`s see how!

Development

Activity 1

• Write on the board 5 and ask what this is?
• Ask, can you tell me its place value? (Units)(Draw place value chart on the board)

• Multiply ‘5’ (already written on the board) by 10, what is it now? (Let students answer 50)
• What is the place value of 5 now? (Tens)
• Multiply this 5 by 100, what will it be? (500)
• What is the place value of 5, now? (Hundreds)
• Wait! What is happening here, can anyone tell me?
• Let students think and share a ‘rule’ that when we multiply a number by 10 or 100, the digit takes higher place value.
• Ask few ore questions like:

• Conclude that this process increase the place value of each digit of a number.
• The same rule applies to decimals as well. Let`s see!
• Write 5 under tenths, and ask what its place value is? (Tenths, 0.5)
• Now multiply by 10, how much increase in the place value? (1 as there is one zero in 10)
• So what will be its new value, 5.0?
• Similarly show the multiplication by 100 and then by 1000.
• Ask can you find steps of multiplication of number with decimal number?

Activity 2

Group Work

• Discuss in groups and find steps to multiply a decimal with 10, 100 or 1000.
• Give them enough time to explain the method to their fellows.
• Let them write the steps in their own wording.
• Once the time is up, ask one representative from each group to read the steps aloud!
• Appreciate the ones whose responses are correct or close to correct.

Activity 3

Teacher`s Input

• Explain the steps verbally and solve one question on the board.
• The steps are written in information for teachers
• Example: Multiply 2.341 by 100. 100 have two zeros. Increase the value of 2.341 by moving the decimal point two places to the right.

Activity 4

Individual Assignments

• Give some question to be done individually. (Choose question from the textbook)
• Ask them to repeat the steps in their mind for every multiplication.
• Allocate time.
• Collect notebooks to assess later.

Sum up / Conclusion

• Conclude the lesson by revising steps of multiplication by giving some examples of multiplication of 10, 100 and 1000.
• The multiplication of decimal fractions is carried out like ordinary multiplication and then decimal point is placed on the same place after adding the number of decimal places of both the numbers in the procedures.
• When you multiply by 10, 100, or 1000 decimal point moves towards right.
• The number of decimal places you move is the same as the number of zeros you are multiplying by.

Assessment

• Give some questions to solve e.g. 7.321 x 10, 3.421 x 100, and 9.633 x 1000
• Complete the following table: