# Lesson Planning of Basic Operations on Decimals

Lesson Planning of Basic Operations on Decimals (Multiplication & Division)

Subject Mathematics

Students` Learning Outcomes

• To multiply a decimal by 2 digit number
• Divide a decimal by a 1-digit number (quotient being a decimal up to two decimal places)

Information for Teachers

• While finding the product of two decimal numbers observe the following steps.
• While dividing a decimal number with 1-digit number and write the answer up to two place of decimals if it can`t divide fully. • Multiply the numbers ignoring the decimal points.
• Count the digits o the right side of the factors and get the “sum”.
• Put the decimal point in the product counting the digits from the right side according to the “sum”.

Material / Resources

Writing board, chalk/marker, duster, paper and pencils for the whole class

Introduction

• There are four operations that we apply do you know what are they? (Expected answer may be as; [+, x, ÷, -]).
• We have done addition and subtraction up till now and now we are going to do multiplication and division.
• First we will revise the multiplication and division done with 10, 100 and 1000 and then we will work out other decimal values with same operation.

Development

 Activity 1 T: Can you still remember how to multiply numbers? Ss: yes/no. T: We`ll start with some simple ones. Can anyone calculate 4 x 5? Ss: 20 T: Why? Ss:? T: What does it mean: Do I have to the number 4 five times? Describe it mathematically in another way. Ss: It means 4 + 4 + 4 + 4 + 4, and that is 20. T: Right, then, what is product of 8 x 3?  Ss: The product of is 8 x 3 = 24 because 8 + 8 = 24. T: Right, but we won`t add/subtract this amount every time. It`s important to know. That multiplication up to 100. Let`s see how are working out? Assign few simple multiplication questions (individual work). Ask do you find any relation between multiplication and division? Ss: the process of multiplication is the inverse of division. Ask for as; 30 ÷ 5 = 6 and 6 x 5 = 30, 100 ÷ 20 = 5 and 20 x 5 = 100. let`s review multiplication with 10, 100, etc. Multiply by powers of 10: T: I know that you can multiply by even bigger number, but these are special numbers! Can you remember the place value table? Draw one I your copy. Think about decimal numbers too. T: What is this table based on? Ss: The system is based on 10. T: what does it mean? Ss: It means that 10 units make 1 ten, 10 tens make 1 hundred … (10 tenths are one unit) T: What difference does it make if the digit 3 is tens or units? Ss: its value is ten times more if it is tens then it is units. T: Add what about if the 3 is hundreds? Ss: Its value is 100 times as much. T: Let`s take 5! I mean, five units: Who can write it in the table? Multiply it by 10 where now? Multiply it by 100 where now? Multiply it by 1000 where now? T: let`s look at the number 32 multiply it by 10, 100, 1000. How does each digit move? Who can state the rule for multiplying by powers of 10? Invite the one student to the board and write the rule and ask another example. Ask “Does this hold for multiplication of decimals as well? let`s see! problem: The thickness of one sheet of card is 0.34 mm, if I have 100 sheets in the shop, how much is the total thickness? Repeat the rule discussed earlier. Demonstrate multiplication on the board, they have also done this in previous session. What about Division? The rule remains the same, but forces inverse as discussed in the beginning, s the rule will be called inverse.  Once with all these extensive discussions are revision are taken place, they are ready for multiplication and division of decimals in more complex manner. Write a number on board , as; 45 Give me a decimal, write on board, as; 0.4 Do the multiplications for 45 x 4 the answer will be 180. Now ask ‘how many digits after decimal in 0.4?’ (Expected answer may be as; one)  T: starting from right, leave one digit and put decimal point, can you tell where the decimal will come? Ss: after one digit from the right side, hence 0. Write another question and repeat the rule and place decimal point. T: you have 2 minutes to do it? Remember the rule: multiply like simple digits (56 x 8 448) and notice how many digits after decimal? One 0.8. hence we will leave one digit from right and put decimal point (44.8)

 Activity 2 Let the class split into groups of not more than 4 in each. Assign a question bank from the textbook. Allocate time and let them drill the skill. Later discuss few questions as the whole class. The whole class discussion: T: we discussed about division in the beginning. T: Does the place value increases or decreases? Ss: yes, decreases and the decimal point move to right. T: What would be the answer of 8.8 ÷ 8? Ss: let then think. T: 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”.

 Activity 3 Individual work: Write some question on board. Repeat the rule with the whole class. Allocate time [15 minutes] Collect notebooks once a;; question are done or / the time is over. Appreciate correct work.

 Activity 4 Textbook activity: Ask students to solve practice questions given in their mathematical work. Repeat the rules for multiplication and division by saying wrong rule. for example, when we multiply with 10 or 100 decimal point moves backward (wrong) Observe how quickly they reply.

Sum up / Conclusion

• While finding the product of two decimal numbers observe the following steps.
• While dividing a decimal number with 1 digit number write the answer up to two place of decimals if it can`t divide fully.
• 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”.

Assessment

Division

0.66 ÷ 2 = _______

0.03 ÷ 3 = ______

0.02 ÷ 2 _______

0.54 ÷ 6 = _____

0.96 ÷ 2 = _____

0.56 ÷ 4 = _____

0.44 ÷ 2 = _____

0.16 ÷ 8 = _____

0.90 ÷ 5 = _____

0.75 ÷ 5 = ____

0.60 ÷ 3 = _____

0.88 ÷ 4 = _____

0.42 ÷ 2 = _____

0.80 ÷ 5 = ______

Multiplication

25 x 0.31 = ______

14 x 0.8 = ______

28 x 0.78 = ______

33 x 0.88 = ______

10 x 0.47 = ______

10 x 0.0 = _______

47 x 0.95 = ______

52 x 0.2 = ______

10 x 0.2 = _______

14 x 0.53 = ______

10 x 0.7 = ______

25 x 0.3 = _______

18 x 0.63 = ______

29 x 0.51 = ______

91 x 0.3 = _________