Lesson Planning of Basic Operations on Decimals

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:

1. Who can write it in the table?
2. Multiply it by 10 where now?
3. Multiply it by 100 where now?
4. Multiply it by 1000 where now?

• T: let`s look at the number 32 multiply it by 10, 100, 1000.

1. How does each digit move?
2. 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.

1. 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.