# MULTIPLICATION AND DIVISION OF DECIMALS

LESSON PLANNING OF MULTIPLICATION AND DIVISION OF DECIMALS WITH WHOLE NUMBERS

Subject Mathematics

Students` Learning Outcomes

• Multiply a decimal with a whole number.
• Divide a decimal with a whole number.

Information for Teachers

Multiplication of decimal number with a whole number:

o   Multiplying with decimals is like multiplying with whole numbers.

o   Multiply just like whole number.

o   Count the numbers right to decimal point in a decimal number.

o   Put the decimal point in the product according to counted numbers from the right side.

Dividing decimal with whole number:

o   Place the decimal straight up from the dividend to the quotient.

o   Divide as normal.

Material / Resources

Writing board, chalk / marker, duster, textbook

Introduction

• Discuss that today we are just thinking about dividing and multiplying when the amount we are dividing or multiplying is not a whole number. E.g.

Development

Activity 1

• Whole class activity, to be done on the board
• Tell that multiplication by a whole number is repeated addition! Try these problems;
• First of all make them do the addition and then tell them about multiplying of decimal number with whole number.

Guided exploration:

• Write a question related to the multiplication of whole numbers on the board.
• Students will compute whole number problem e.g.24 x 63 = 1512

Teacher`s input:

• Discuss about the steps of solving each problem.
• Model process of estimating prior to solving
• Show the process using traditional method.
• Model / demonstrate how to place a decimal appropriately –using estimation.

Guided practice:

• Students will follow all steps to solve problems and will a share with whole class. (Textbook sum)
• Independent Practice (Copy work)
• Students work on question bank to practice multiplying with decimals.

Activity 3

Whole Class Discussion:

• Write a number on the board for example 45.
• Write another number (0.4) on the board
• Do the multiplications for 45 x 4 the answer will be 180. Now ask ‘How many digits are there after decimal in 0.4? (One)
• Tell them starting from right, leave one digit and put decimal point. Can you tell where the decimal will come? After 0 from right, hence 18.0
• Write another question and repeat the rule and place decimal point.
• Tell them that they have 2 minutes to do it?
• Remember the rule:  multiply like simple digits (56 x 8 =448) and notice how many digits are there after decimal? (One) Hence we will leave one digit from right and put decimal point. (44.8)

Activity 3

Group Work:

o   Let the class split into groups of not more than 4 in each.

o   Assign a question bank from the textbook

o   Allocate time and let them ‘Drill the Skill’

o   Later discuss few questions as a whole class.

For example:

o   Ask students what would be the answer of 88 ÷ 8? (11)

o   Now ask what would be the answer of 8.8 ÷ 8? (1.1)

o   Let them think and try.

o   Tell them the rule is Proceed with the division as you normally would except put the decimal point in the answer or quotient exactly above where it occurs in the dividend.

Introduce steps to dividing decimal numbers by whole numbers:

o   When dividing a decimal by a whole number, place the decimal in the quotient straight above the decimal in the divided. Next divide.

o   Model two examples of writing the problem-placing the decimal straight up and dividing

o   In one example show what happens when you still have a “remainder” and continue to add zeros until the number is complete.

Guided Practice:

• Students practice two examples-one with a decimal that terminates and one in which zeros need to be added.
• Students review writing division in different ways-and translate problems into different formats.
• Students practice independently.
• Collect notebooks once all questions are done or time up!

Sum up / Conclusion

• Multiplication of decimal with a whole number:

Multiplying with decimals is like multiplying with whole number.

Multiply just like whole number.

Count the numbers right to decimal point in a decimal number.

Put the decimal point in the product according to counted numbers from the right side.

• Dividing decimal with whole number:

Place the decimal straight up from the dividend to the quotient.

Divide as normal division.

Assessment

• Take some Questions from the textbook to assess students` learning.
• Give some questions from textbook to solve individually.
• The thickness of a plastic sheet is 0.56 mm, what will be the total thickness of the 15 same type of sheets.

• Use estimation to help you select the correct quotient in the following: