Lesson Notes By Weeks and Term v5 - Grade 2

Lesson Video

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Performance objectives

• Identify and represent numbers 0-99 with blocks.
• Break down numbers into tens and units.
• Compare and order numbers from 0-99.
• Add single-digit numbers to two-digit numbers.
• Use number names and symbols.

Lesson summary

This week, we're diving into the exciting world of numbers between 0 and 99! Understanding these numbers is super important because we use them every day, everywhere – from counting sweets in our lunchboxes to figuring out how much money we need to buy an ice cream at the spaza shop down the street. This week, we will focus on understanding what each digit in a number means (place value) and start practicing simple addition. It’s the foundation for all the bigger maths problems you'll solve in the future! Imagine you're saving up for a soccer ball; knowing how to count and add your money will help you reach your goal.

Lesson notes

2.1 Understanding Place Value (Tens and Units) Every number has a place value. Place value tells us the value of each digit in a number. For numbers between 0 and 99, we have two important places: Tens Place: This tells us how many groups of ten are in the number.

Units Place (Ones Place): This tells us how many individual units (ones) are in the number. Let’s think about the number

4

7. The digit 4 is in the tens place. This means we have 4 groups of ten, or

4

0. The digit 7 is in the units place. This means we have 7 individual units. So, 47 is made up of 4 tens and 7 units.

Example 1: Representing Numbers with Base-Ten Blocks Imagine we have base-ten blocks. A "long" block represents ten, and a small "cube" represents one. To represent the number 32, we would use: 3 long blocks (3 tens = 30) 2 cube blocks (2 units = 2) Therefore, 30 + 2 = 32 Example 2: Decomposing Numbers Decomposing a number means breaking it down into its tens and units.

Let's decompose the number 65: 65 = 6 tens + 5 units 65 = 60 + 5 2.2 Comparing and Ordering Numbers When comparing numbers, we want to know which one is bigger (greater than), smaller (less than), or if they are the same (equal to). Greater Than (>): A number is greater than another if it is further to the right on a number line. *Less Than ( 23 (32 is greater than 23) Or, 23 < 32 (23 is less than 32)

Example 4: Ordering Numbers Let's order these numbers from smallest to largest: 15, 8, 24, 11 Look at the tens place. Some numbers have 0 tens (8), and some have 1 ten (15, 11), and one has 2 tens (24). 8 will be the smallest. Comparing 15 and 11, they both have one ten.

Compare the units place: 5 is bigger than

1. So, 11 is smaller than

1

5. The correct order is: 8, 11, 15, 24 2.3 Adding Single-Digit Numbers to Two-Digit Numbers (Without Carrying Over) Adding without carrying over means that when we add the units place, the answer is less than

1

0. Let’s say we have 23 +

4. Write the numbers on top of each other, lining up the units place: ``` 23 + 4 ---- ``` Add the units place: 3 + 4 = 7 Write the 7 in the units place in the answer. The tens place in 23 is

2. We don't add anything to it, so we just bring it down. ``` 23 + 4 ---- 27 ``` Therefore, 23 + 4 = 27 Example 5: Addition without carrying over Let's add 52 + 6 Write the numbers in columns: ``` 52 + 6 ---- ``` Add the units: 2 + 6 = 8 Write 8 in the units place in the answer.

Bring the 5 down: ``` 52 + 6 ---- 58 ``` Therefore, 52 + 6 = 58 Guided Practice (With Solutions)

Question 1: Represent the number 56 using base-ten blocks. How many longs (tens) and cubes (units) will you need?

Solution: 56 has 5 tens and 6 units.

Therefore, you need 5 long blocks (representing 50) and 6 cube blocks (representing 6).

Commentary: This question directly tests the understanding of place value and its visual representation.

Question 2: Decompose the number 81 into tens and units.

Solution: 81 = 8 tens + 1 unit 81 = 80 + 1

Commentary: This reinforces the concept of decomposing numbers, a foundational skill for later arithmetic.

Question 3: Which number is greater, 45 or 54? Explain your reasoning.

Solution: 54 is greater than

4

5. Reasoning: 54 has 5 tens, while 45 only has 4 tens. Since 5 tens (50) is more than 4 tens (40), 54 is greater.

Commentary: This checks the ability to compare numbers based on place value.

Question 4: Calculate 35 +

2. Solution: ``` 35 + 2 37 ``` 35 + 2 = 37

Commentary: This is a simple addition problem to practice adding a single-digit number to a two-digit number without carrying over.

Question 5: Write the number 79 using number names.

Solution: Seventy-nine

Commentary: This assesses students' ability to connect numerical symbols with their verbal representation. Independent Practice (Questions Only) Represent the number 28 using base-ten blocks. Decompose the number 93 into tens and units. Which number is less, 61 or 16? Explain your reasoning. Order these numbers from largest to smallest: 37, 19, 42, 25 Calculate 63 +

5. Calculate 41 +

7. What number has 7 tens and 3 units? What number has 2 tens and 0 units? Write it down. Write the number 51 using number names. Write the number eighty-six using digits.