Lesson Notes By Weeks and Term v5 - Grade 3
Numbers 0–999: place value and operations (Grade 3) – Week 4 focus
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Numbers 0–999: place value and operations (Grade 3) – Week 4 focus
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Subject: Mathematics
Class: Grade 3
Term: 1st Term
Week: 4
Theme: General lesson support
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This week, we will continue our exploration of numbers up to 999, focusing on place value and how we use this knowledge to add and subtract. Understanding place value is crucial because it forms the foundation for all future math skills. It allows us to understand the value of each digit in a number, which is essential for accurately performing addition, subtraction, multiplication, and division.
Think about it: when you go to the local spaza shop to buy sweets, you need to be able to count your money and understand what each coin and note is worth! This understanding relies on knowing place value.
Place Value: The Value of Where a Digit Lives Every digit in a number has a place value, which tells us how much that digit is worth. In numbers up to 999, we have three main place values: Hundreds (H): The digit in the hundreds place tells us how many groups of one hundred there are. For example, in the number 325, the '3' is in the hundreds place, meaning there are three hundreds (300).
Tens (T): The digit in the tens place tells us how many groups of ten there are. For example, in the number 325, the '2' is in the tens place, meaning there are two tens (20).
Ones (O): The digit in the ones place tells us how many individual units there are. For example, in the number 325, the '5' is in the ones place, meaning there are five ones (5).
Decomposing Numbers: Decomposing a number means breaking it down into the sum of its place values. This helps us understand the composition of the number and makes addition and subtraction easier.
Example: Let's decompose the number 472. 4 is in the hundreds place, so it represents 400. 7 is in the tens place, so it represents 70. 2 is in the ones place, so it represents
2. Therefore, 472 = 400 + 70 +
2. Addition (Without Regrouping): When adding numbers without regrouping, we add the digits in each place value column separately, starting with the ones, then the tens, and finally the hundreds. Regrouping (carrying over) will be covered in a later lesson.
Example: Let's add 234 and 152. ``` H T O 2 3 4 + 1 5 2 3 8 6 ``` Ones: 4 + 2 = 6 Tens: 3 + 5 = 8 Hundreds: 2 + 1 = 3 So, 234 + 152 =
3
8
6. Subtraction (Without Regrouping): When subtracting numbers without regrouping, we subtract the digits in each place value column separately, starting with the ones, then the tens, and finally the hundreds. Borrowing will be covered in a later lesson.
Example: Let's subtract 123 from 456. ``` H T O 4 5 6 1 2 3 3 3 3 ``` Ones: 6 - 3 = 3 Tens: 5 - 2 = 3 Hundreds: 4 - 1 = 3 So, 456 - 123 =
3
3
3. Why this matters: Imagine you're helping your family sell vetkoek at a local market. You need to add up the money you've made from each sale and subtract the cost of ingredients to see how much profit you’ve made. Understanding place value and addition/subtraction is vital for this! Guided Practice (With Solutions)
Question 1: What is the place value of the digit '7' in the number 671?
Solution: The digit '7' is in the tens place.
Therefore, its place value is
7
0. Commentary: This question directly assesses the understanding of place value. Students need to correctly identify the position of the digit within the number.
Question 2: Decompose the number 528 into its place value components.
Solution: 528 = 500 + 20 + 8
Commentary: This question tests the ability to break down a number based on place value. Students need to understand that each digit contributes to the overall value of the number based on its position.
Question 3: Calculate 315 +
2
4
3. Solution: ``` H T O 3 1 5 + 2 4 3 5 5 8 ``` Ones: 5 + 3 = 8 Tens: 1 + 4 = 5 Hundreds: 3 + 2 = 5 Therefore, 315 + 243 =
5
5
8. Commentary: This problem reinforces addition without regrouping. Students should follow the column-wise addition procedure.
Question 4: Calculate 687 -
2
5
4. Solution: ``` H T O 6 8 7 2 5 4 4 3 3 ``` Ones: 7 - 4 = 3 Tens: 8 - 5 = 3 Hundreds: 6 - 2 = 4 Therefore, 687 - 254 =
4
3
3. Commentary: This problem focuses on subtraction without regrouping. Similar to addition, students should follow the column-wise subtraction procedure.
Question 5: Thando has 231 marbles, and Sindi has 145 marbles. How many marbles do they have altogether?
Solution: We need to add the number of marbles Thando and Sindi have: 231 + 145 ``` H T O 2 3 1 + 1 4 5 3 7 6 ``` Therefore, Thando and Sindi have 376 marbles altogether.
Commentary: This is a simple word problem requiring addition. Students need to identify the operation (addition) from the context of the problem. Independent Practice (Questions Only) What is the place value of the digit '4' in the number 849? Decompose the number 916 into its place value components. Calculate 427 +
3
5
2. Calculate 798 -
4
6
5. Nomusa has 512 beads. She gives 201 beads to her friend. How many beads does Nomusa have left? Write the number that has 6 hundreds, 3 tens, and 0 ones. What number is 10 more than 349? What number is 100 less than 856? John collected 243 cans for recycling, and Mary collected 325 cans. How many cans did they collect in total? A farmer had 678 oranges. He sold 34 at the market. How many oranges does he have left?