Lesson Notes By Weeks and Term v5 - Grade 3

Lesson Video

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Performance objectives

• Identify the place value of digits in a 3-digit number.
• Decompose 3-digit numbers into hundreds, tens, and ones.
• Add two 3-digit numbers with carrying over.
• Subtract two 3-digit numbers with borrowing.
• Solve word problems using addition and subtraction.

Lesson summary

This week, we will delve deeper into understanding numbers from 0 to

9

9

9. We will focus on place value (hundreds, tens, and ones) and using this knowledge to perform addition and subtraction. Understanding these concepts is crucial because numbers are everywhere! From counting money at the shop to measuring ingredients while baking vetkoek with your grandmother, strong number sense helps us in our everyday lives. In South Africa, being able to handle numbers confidently is vital for managing our finances, understanding prices, and participating fully in our community.

Lesson notes

Understanding Place Value: Every digit in a number has a place value, which tells us its worth. In a 3-digit number, we have: Hundreds (H): The digit in the hundreds place tells us how many groups of one hundred there are.

Tens (T): The digit in the tens place tells us how many groups of ten there are.

Ones (O): The digit in the ones place tells us how many single units there are.

Example: In the number 528: The digit 5 is in the hundreds place, so it represents 500 (5 hundreds). The digit 2 is in the tens place, so it represents 20 (2 tens). The digit 8 is in the ones place, so it represents 8 (8 ones).

We can write this as: 528 = 500 + 20 +

8. This is called expanded form. Addition of 3-Digit Numbers with Carrying Over: When adding, we start with the ones column. If the sum of the digits in the ones column is 10 or more, we need to carry over to the tens column. Similarly, if the sum of the digits in the tens column (including any carried over digit) is 10 or more, we carry over to the hundreds column.

Example: 257 + 185 Write the numbers vertically, aligning the place values: ``` 257 + 185 ------- ``` Add the ones column: 7 + 5 =

1

2. Write down the 2 in the ones place and carry over the 1 to the tens column. ``` 1 257 + 185 ------- 2 ``` Add the tens column (including the carried over 1): 1 + 5 + 8 =

1

4. Write down the 4 in the tens place and carry over the 1 to the hundreds column. ``` 11 257 + 185 ------- 42 ``` Add the hundreds column (including the carried over 1): 1 + 2 + 1 =

4. Write down the 4 in the hundreds place. ``` 11 257 + 185 ------- 442 ``` Therefore, 257 + 185 =

4

4

2. Subtraction of 3-Digit Numbers with Borrowing: When subtracting, if the digit in the top number is smaller than the digit in the bottom number in a specific column, we need to borrow from the column to the left.

Example: 432 - 178 Write the numbers vertically, aligning the place values: ``` 432 178 ------- ``` Subtract the ones column: 2 -

8. We can't subtract 8 from 2, so we need to borrow 1 ten from the tens column. This makes the 3 in the tens column become 2, and the 2 in the ones column becomes 12. ``` 4 2 12 4 3 2 1 7 8 ------- ``` Subtract the ones column: 12 - 8 =

4. Write down the 4 in the ones place. ``` 4 2 12 4 3 2 1 7 8 ------- 4 ``` Subtract the tens column: 2 -

7. We can't subtract 7 from 2, so we need to borrow 1 hundred from the hundreds column. This makes the 4 in the hundreds column become 3, and the 2 in the tens column becomes 12. ``` 3 12 12 4 3 2 1 7 8 ------- 4 ``` Subtract the tens column: 12 - 7 =

5. Write down the 5 in the tens place. ``` 3 12 12 4 3 2 1 7 8 ------- 5 4 ``` Subtract the hundreds column: 3 - 1 =

2. Write down the 2 in the hundreds place. ``` 3 12 12 4 3 2 1 7 8 ------- 2 5 4 ``` Therefore, 432 - 178 =

2

5

4. Guided Practice (With Solutions)

Question 1: What is the place value of the digit 7 in the number 673?

Solution: The digit 7 is in the tens place.

Therefore, its place value is

7

0. Commentary: This question directly addresses objective

1. Learners need to identify the position of the digit to determine its value.

Question 2: Write the number 816 in expanded form.

Solution: 816 = 800 + 10 + 6

Commentary: This question targets objective

2. This tests the learner's understanding of how to break down a number into its constituent place values.

Question 3: Calculate 368 +

2

5

4. Solution: ``` 1 1 368 + 254 622 ``` Therefore, 368 + 254 =

6

2

2. Commentary: This question aligns with objective

3. It requires addition with carrying over from the ones to the tens and from the tens to the hundreds.

Question 4: Calculate 521 -

2

8

7. Solution: ``` 4 11 11 5 2 1 2 8 7 2 3 4 ``` Therefore, 521 - 287 =

2

3

4. Commentary: This question focuses on objective 4 and reinforces subtraction skills with borrowing. Borrowing occurs both from the tens to the ones and the hundreds to the tens.

Question 5: Sipho has 145 marbles. Thando has 236 marbles. How many marbles do they have altogether?

Solution: This is an addition problem. We need to add 145 and 236. ``` 145 + 236 381 ``` They have 381 marbles altogether.

Commentary: This is a word problem (objective 5) requiring the application of addition in a real-world context. Independent Practice (Questions Only) What is the place value of the digit 4 in the number 941? Write the number 709 in expanded form. Calculate 427 +

3

9

5. Calculate 613 -

2

5

8. A farmer has 215 chickens and buys 138 more. How many chickens does the farmer have in total? A bakery made 350 koeksisters. They sold 175 koeksisters. How many koeksisters are left? Write the following number in expanded form: 555 Sarah has 234 beads. Peter has 456 beads. How many more beads does Peter have than Sarah? What number is 200 + 50 + 7? Jane scored 123 points on level one of her video game. She scored 342 points on level two of her video game. How many points did Jane score altogether?