Lesson Notes By Weeks and Term v5 - Grade 2
Numbers 0–99: place value and operations (Grade 2) – Week 3 focus
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Numbers 0–99: place value and operations (Grade 2) – Week 3 focus
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Subject: Mathematics
Class: Grade 2
Term: 1st Term
Week: 3
Theme: General lesson support
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This week, we're diving deeper into numbers from 0 to 99, focusing on understanding place value and how it helps us with addition and subtraction. Understanding place value is super important because it helps us understand how much each digit in a number is really worth. This is useful in everyday life, like when we're buying sweets at the spaza shop or saving our pocket money. For example, when we see the number 23, knowing place value helps us realize that it's not just two and three, but two groups of ten and three individual ones. This understanding makes adding and subtracting much easier!
Place Value: Tens and Units Every number is made up of digits, and each digit has a place value. In numbers from 0 to 99, we have two main place values: Tens: This is the digit that tells us how many groups of ten we have. For example, in the number 32, the digit 3 is in the tens place, meaning we have 3 groups of ten (30).
Units (Ones): This is the digit that tells us how many individual ones we have. For example, in the number 32, the digit 2 is in the units place, meaning we have 2 individual ones. We can represent this using concrete materials like base-ten blocks (longs for tens and cubes for units) or even just drawing sticks and dots.
Example 1: Let's represent the number
4
5. We have 4 in the tens place, so we have 4 tens (40). We can represent this with 4 long sticks. We have 5 in the units place, so we have 5 ones (5). We can represent this with 5 dots.
Therefore, 45 = 40 + 5 Example 2: What is the value of the digit 7 in the number 78? The digit 7 is in the tens place. This means it represents 7 tens, which is
7
0. Decomposing Numbers Decomposing a number means breaking it down into its tens and units. This helps us understand its place value and makes addition and subtraction easier.
Example 1: Decompose the number 61. 61 has 6 tens (60) and 1 unit (1). So, 61 = 60 + 1 Example 2: Decompose the number 29. 29 has 2 tens (20) and 9 units (9). So, 29 = 20 + 9 Addition without Carrying Over When adding two-digit numbers without carrying over, we add the units place first, then the tens place. It's like combining the tens and then combining the ones!
Example 1: Calculate 23 + 14 Units Place: 3 + 4 = 7 Tens Place: 2 + 1 = 3 Combine: 3 tens and 7 units = 37 Therefore, 23 + 14 = 37 Example 2: Calculate 52 + 36 Units Place: 2 + 6 = 8 Tens Place: 5 + 3 = 8 Combine: 8 tens and 8 units = 88 Therefore, 52 + 36 = 88 Subtraction without Borrowing When subtracting two-digit numbers without borrowing, we subtract the units place first, then the tens place. We're taking away the tens and taking away the ones.
Example 1: Calculate 48 - 25 Units Place: 8 - 5 = 3 Tens Place: 4 - 2 = 2 Combine: 2 tens and 3 units = 23 Therefore, 48 - 25 = 23 Example 2: Calculate 67 - 32 Units Place: 7 - 2 = 5 Tens Place: 6 - 3 = 3 Combine: 3 tens and 5 units = 35 Therefore, 67 - 32 = 35 Guided Practice (With Solutions)
Question 1: What is the value of the underlined digit: 5 9 ?
Solution: The underlined digit is
9. It's in the units place.
Therefore, its value is
9. Commentary: This question directly addresses LO1, focusing on identifying the place value of a digit.
Question 2: Decompose the number 74 into tens and units.
Solution: 74 has 7 tens and 4 units.
Therefore, 74 = 70 +
4. Commentary: This question focuses on LO2, decomposing a number based on place value.
Question 3: Calculate 31 +
2
5. Solution: Units Place: 1 + 5 = 6 Tens Place: 3 + 2 = 5 Combine: 5 tens and 6 units = 56 Therefore, 31 + 25 = 56
Commentary: This question targets LO3, adding two 2-digit numbers without carrying.
Question 4: Calculate 68 -
4
3. Solution: Units Place: 8 - 3 = 5 Tens Place: 6 - 4 = 2 Combine: 2 tens and 5 units = 25 Therefore, 68 - 43 =
2
5. Commentary: This question addresses LO4, subtracting two 2-digit numbers without borrowing.
Question 5: Thando has 42 marbles, and Sipho has 27 marbles. How many marbles do they have together?
Solution: This is an addition problem. We need to add 42 and
2
7. Units place: 2 + 7 = 9 Tens place: 4 + 2 = 6 Combine: 6 tens and 9 units = 69 Therefore, Thando and Sipho have 69 marbles together.
Commentary: This question addresses LO5, applying place value understanding to solve a word problem. Independent Practice (Questions Only)
What is the value of the underlined digit: 8 2? Decompose the number 96 into tens and units. Calculate 17 +
3
2. Calculate 45 +
2
3. Calculate 59 -
1
6. Calculate 78 -
5
5. Zanele has 34 stickers, and she gives 12 to her friend. How many stickers does Zanele have left? A shop sells 65 apples and 24 oranges. How many more apples than oranges are there? Write down the number that has 6 tens and 3 ones.
Which number is bigger: 49 or 94? Explain why.