Lesson Notes By Weeks and Term v3 - Primary 2
Subtraction
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Subtraction
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Subject: General Mathematics
Class: Primary 2
Term: 1st Term
Week: 3
Theme: Basic Operations
This page supports the lesson note with a companion video and a short classroom-ready summary.
For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.
Watch on YouTubesubtract 2-digit numbers with out exchanging or renaming; subtract 2-digit numbers with exchanging and renaming; apply addition and subtraction in everyday activities.
Basic Operations 11 9 1 - 3 5 ----- ``` Units: 11 - 5 =
6. Tens: 8 - 3 = 5. ``` T U 8 11 9 1 - 3 5 ----- 5 6 ``` Answer: Mummy Ngozi has N56 left.
Commentary: Real-life money management scenario, crucial for financial literacy.
5. Independent Practice (Questions Only)
Solve the following: 1. `59 - 24 = ?` 2. `76 - 31 = ?` 3. `87 - 15 = ?`
4. A school bus had 65 children. If 20 children dropped off at the first stop, how many children are still on the bus? 5. `42 - 18 = ?` 6. `60 - 34 = ?` 7. `95 - 67 = ?`
8. Baba Kemi had 73 chickens. He sold 49 chickens. How many chickens does he have left?
9. There are 54 mangoes on a tree. If 26 mangoes fall off due to wind, how many mangoes are left on the tree?
1
0. Mention two everyday activities where you need to subtract numbers accurately.
6. Evaluation and Assessment Formative Assessment: Observe student participation during class activities and discussions. Monitor students' work on slates during guided practice, providing immediate feedback. Ask targeted questions to check for understanding of key concepts (e.g., "Why did we 'borrow' in this problem?").
Summative Assessment: The following questions directly align with the provided evaluation guide:
1. Subtract 2-digit numbers without exchanging or renaming.
Calculate: `87 - 34 = ?` (Expected Answer: 53)
Marking: 1 mark for correct units, 1 mark for correct tens. Total 2 marks.
2. Subtract 2-digit numbers with exchanging and renaming.
Calculate: `73 - 48 = ?` (Expected Answer: 25)
Marking: 1 mark for showing correct renaming/exchange, 1 mark for correct units, 1 mark for correct tens. Total 3 marks.
3. Mention 4 everyday activities where accuracy is needed (involving addition and/or subtraction). (Expected Answers may include: giving/receiving correct change in the market, counting farm produce, sharing items equally, measuring ingredients for cooking, managing pocket money, counting remaining inventory in a shop, keeping score in a game, telling the correct time difference.)
Marking: 1 mark for each relevant activity mentioned. Total 4 marks.
Total Marks: 9 marks
7. Real-life Applications / Integration
1. Market Transactions: Subtraction is crucial for calculating change after a purchase. For example, if a child buys an item for N45 with a N100 note, they need to subtract N45 from N100 to determine the correct change (N55). It is also used to determine how much money is left after buying multiple items.
2. Farming and Inventory Management: Farmers use subtraction to count how many crops are left after selling a portion, or how many seedlings remain after planting. A small shop owner uses subtraction to track how many items (e.g., sachets of milk, loaves of bread) are left in stock after sales.
3. Community and Household Budgeting: Families use subtraction to manage household expenses. For example, knowing how much money is left from a budget after paying for school fees or food. In community events, subtraction can help determine how many people attended versus how many were expected, or how many plates of food are left.
4. Time and Age Differences: Calculating age differences between siblings or friends, or determining how many days are left until an event, relies on subtraction.
8. Differentiation, Remediation and Extension 8.
1. Remediation (for struggling learners): Concrete Manipulatives: Provide abundant hands-on materials (e.g., bundles of straws, bottle tops, beads) for every subtraction problem. Guide them to physically "take away" or "exchange" tens for units.
Number Line: Use a large number line for visual learners to count backwards, especially for problems without renaming, before moving to the column method.
Focused Practice: Start with simpler two-digit subtraction problems that do not require exchanging until mastery is achieved. Gradually introduce exchanging with smaller numbers (e.g., 21 - 7).
Visual Aids: Provide worksheets with pre-drawn place value charts or columns to help students align numbers correctly. Use different colours for units and tens columns.
Peer Tutoring/Small Group Instruction: Pair struggling learners with stronger peers the 5 bundles, opening it up into 10 single sticks. Now we have 4 bundles of ten and 12 single sticks." Then, physically remove 7 single sticks from the 12 and 2 bundles of ten from the
4. Count the remainder. Translate this process to the vertical written method on the board, clearly showing how the numbers in the tens and units columns are changed (crossed out and written above). Emphasize that "borrowing" means "exchanging 1 ten for 10 units." Provide 2-3 additional examples, guiding students step-by-step.
Student Activity: Actively participate in the manipulative demonstration, asking clarifying questions. Work in pairs to solve problems with exchanging using their own manipulatives (if available) or by drawing representations. Solve problems independently on their slates/notebooks, showing the renaming process. 3.
4. Real-life Applications (10 minutes)
Teacher Activity: Lead a discussion on where addition and subtraction are used in everyday Nigerian life.
Prompt students with scenarios: "When your mother buys food at the market, how does she know how much change she should get?" "If you have 15 pencils and lose 3, how many are left?" Student Activity: Students share examples from their experiences, relating subtraction to buying/selling, sharing, counting, and budgeting.
4. Guided Practice (With Solutions)
1. Question: A farmer harvested 68 corn cobs. He sold 34 of them at the local market. How many corn cobs are left?
Solution: This problem involves subtraction without exchanging. ``` T U 6 8 - 3 4 ----- ``` Subtract units: 8 - 4 =
4. Subtract tens: 6 - 3 = 3. ``` T U 6 8 - 3 4 ----- 3 4 ``` Answer: 34 corn cobs are left.
Commentary: This reinforces subtraction without exchanging, using a common Nigerian agricultural context.
2. Question: There are 75 students in Primary
2. If 40 students went for a sports event, how many students remained in the classroom?
Solution: This is another problem without exchanging. ``` T U 7 5 - 4 0 ----- ``` Subtract units: 5 - 0 =
5. Subtract tens: 7 - 4 = 3. ``` T U 7 5 - 4 0 ----- 3 5 ``` Answer: 35 students remained in the classroom.
Commentary: Simple subtraction without renaming, good for building confidence.
3. Question: A local shopkeeper had 43 bags of groundnut. She sold 28 bags. How many bags of groundnut does she have left?
Solution: This problem involves subtraction with exchanging. ``` T U 4 3 - 2 8 ----- ``` Units: We cannot subtract 8 from
3. Exchange: Take 1 ten from the 4 tens (leaving 3 tens). Add 10 units to the 3 units (making 13 units). ``` T U 3 13 4 3 - 2 8 ----- ``` Units: 13 - 8 =
5. Tens: 3 - 2 = 1. ``` T U 3 13 4 3 - 2 8 ----- 1 5 ``` Answer: She has 15 bags of groundnut left.
Commentary: This is a clear example of the borrowing process with local context.
4. Question: Mummy Ngozi had N
9
1. She spent N35 to buy yam and plantain. How much money does she have left?
Solution: This problem involves subtraction with exchanging. ``` T U 9 1 - 3 5 ----- ``` Units: We cannot subtract 5 from
1. Exchange: Take 1 ten from the 9 tens (leaving 8 tens). Add 10 units to the 1 unit (making 11 units). ``` T U 8 11 9 1 - 3 5 ----- ``` Units: 11 - 5 =
6. Tens: 8 - 3 = 5. ``` T U 8 11 9 1 - 3 5 ----- 5 6 ``` Answer: Mummy Ngozi has N56 left.
Commentary: Real-life money management scenario, crucial for financial literacy.
5. Independent Practice (Questions Only)
Solve the following: 1. `59 - 24 = ?` 2. `76 - 31 = ?` 3. `87 - 15 = ?`
4. A school bus had 65 children. If 20 children dropped off at Subtraction Term: 1st Term Week: 4 ---
1. Overview and Learning Objectives This topic focuses on the fundamental operation of subtraction, building upon learners' prior knowledge of numbers and single-digit subtraction. Subtraction is a critical skill for daily life, enabling individuals to determine remaining quantities, calculate differences, and manage resources effectively. Understanding subtraction is essential for practical activities such as managing money, sharing items, calculating stock, and understanding changes in quantities. Upon completion of this lesson, students will be able to: Subtract two-digit numbers without needing to exchange or rename (i.e., without "borrowing"). Subtract two-digit numbers by exchanging or renaming (i.e., "borrowing") from the tens place. Identify and describe various real-life situations where the concepts of addition and subtraction are applied. This knowledge is crucial for everyday activities in Nigeria, such as accurately giving or receiving change in markets, managing small allowances, determining how many items are left after some have been used or sold, and calculating differences in quantities of goods or people within their communities.
2. Key Concepts and Explanations 2.
1. Definition of Subtraction Subtraction is one of the four basic arithmetic operations. It involves taking away one number from another, finding the difference between two numbers, or determining how much is left after a portion has been removed.
Minuend: The number from which another number is subtracted (the larger number).
Subtrahend: The number being subtracted (the smaller number).
Difference: The result obtained after subtracting the subtrahend from the minuend. The symbol for subtraction is the minus sign (-). 2.
2. Place Value Review Before performing two-digit subtraction, students must have a solid understanding of place value (Units and Tens).
Units (U): Represents single items (0-9).
Tens (T): Represents groups of ten (e.g., 1 ten = 10 units, 2 tens = 20 units). When subtracting two-digit numbers, numbers are arranged vertically, aligning the units digits and tens digits. Subtraction always begins from the units column, moving to the tens column. 2.
3. Subtraction of 2-Digit Numbers without Exchanging/Renaming This type of subtraction occurs when the units digit of the minuend is greater than or equal to the units digit of the subtrahend, and similarly for the tens digits. No "borrowing" is required.
Step-by-step Example 1: `45 - 23` Context: A hawker had 45 oranges and sold 23 of them. How many oranges are left?
Step 1: Arrange the numbers vertically, aligning by place value. ``` T U 4 5 (Minuend) - 2 3 (Subtrahend) ----- ``` Step 2: Subtract the units digits.
Subtract 3 units from 5 units: 5 - 3 = 2 units. Write 2 in the units column of the answer. ``` T U 4 5 - 2 3 ----- 2 ``` Step 3: Subtract the tens digits.
Subtract 2 tens from 4 tens: 4 - 2 = 2 tens. Write 2 in the tens column of the answer. ``` T U 4 5 - 2 3 ----- 2 2 ``` Result: 22 oranges are left. 2.
4. Subtraction of 2-Digit Numbers with Exchanging/Renaming ("Borrowing") This type of subtraction is required when a digit in the minuend is smaller than the corresponding digit in the subtrahend, starting from the units column. In such cases, one 'ten' is exchanged from the tens column of the minuend and converted into 'ten units', which are then added to the units column of the minuend.
Step-by-step Example 2: `52 - 27` Context: A baker prepared 52 loaves of bread. By afternoon, 27 loaves were sold. How many loaves are remaining?
Step 1: Arrange the numbers vertically, aligning by place value. ``` T U 5 2 (Minuend) - 2 7 (Subtrahend) ----- ``` Step 2: Subtract the units digits. Try to subtract 7 units from 2 units (2 - 7). This is not possible in basic subtraction as 2 is smaller than
7. Step 3: Exchange/Rename (Borrow) from the tens column. Go to the tens column of the minuend (which has 5 tens). * Take 1 ten from the 5 tens, leaving 4 tens. Cross out 5 and write 4 above it.