Lesson Notes By Weeks and Term v5 - Grade 4
Whole numbers: place value and operations (Grade 4) – Week 3 focus
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Whole numbers: place value and operations (Grade 4) – Week 3 focus
Download the Lessonotes Mobile South Africa app for faster lesson access on Android and iPhone.
Subject: Mathematics
Class: Grade 4
Term: 1st Term
Week: 3
Theme: General lesson support
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This week, we continue our exciting journey with whole numbers! We will focus on two very important skills that we use almost every day: rounding off numbers and adding or subtracting large numbers. Think about going shopping at Pick n Pay or Shoprite. The till slip shows the total, which is addition. When you pay with cash, the change you get back is calculated using subtraction. Rounding helps us to quickly guess or estimate if we have enough money. For example, if a bag of chips costs R18.99, we can round it to R20 to quickly add up our total.
A. Rounding Off Whole Numbers Why do we round off? Rounding makes big or complicated numbers simpler and easier to work with. It's a way of finding a number that is close to the original number. We use it to estimate.
The Rule of Rounding: Identify the place value you are rounding to (e.g., the tens, hundreds, or thousands place). Look next door to the digit on the right. If the digit on the right is 5, 6, 7, 8, or 9, you round up. The digit in your rounding place goes up by one. If the digit on the right is 0, 1, 2, 3, or 4, you round down (or stay the same). The digit in your rounding place stays the same. All the digits to the right of the rounding place become zeros.
Example 1: Rounding to the nearest 10
A family travels 47 km from their home in Soweto to the Cradle of Humankind. Round this distance to the nearest 10 km.
The number is
4
7.
We are rounding to the nearest ten. The digit in the tens place is
4.
Look next door to the right. The digit is
7.
Since 7 is 5 or more, we round up.
The tens digit (4) goes up to
5.
The digit to the right (7) becomes a
0.
So, 47 km rounded to the nearest 10 is 50 km.
Example 2: Rounding to the nearest 100
A primary school in Gqeberha has 362 learners. Round this to the nearest
1
0
0.
The number is
3
6
2.
We are rounding to the nearest hundred. The digit is
3.
Look next door. The digit is
6.
Since 6 is 5 or more, we round up.
The hundreds digit (3) goes up to
4.
All digits to the right (6 and 2) become zeros.
So, 362 rounded to the nearest 100 is
4
0
0. Example 3: Rounding to the nearest 1000
The uKhahlamba-Drakensberg Park is 2428 square kilometres. Round this area to the nearest
1
0
0
0.
The number is
2
4
2
8.
We are rounding to the nearest thousand. The digit is
2.
Look next door. The digit is
4.
Since 4 is 4 or less, we round down.
The thousands digit (2) stays the same.
All digits to the right (4, 2, and 8) become zeros.
So, 2428 rounded to the nearest 1000 is
2
0
0
0.
B. Addition and Subtraction using the Column Method
The column method is a neat way to add and subtract large numbers by lining them up according to their place value (Units, Tens, Hundreds, Thousands).
Worked
Example: Addition with Carrying
A farmer in Limpopo harvested 2573 bags of mielies in the first week and 1845 bags in the second week. How many bags did he harvest in total?