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Operations
Standard 5 Mathematics: Operations
Module 1: Numbers and Operation — Lesson 2: Addition, subtraction, multiplication, division, estimation, factors, LCM, HCF and order of operations.
Slide 1 / 12
Welcome ➕➖✖️➗
Today we learn how to apply the four basic operations on whole numbers
The four basic operations are:
Addition, Subtraction, Multiplication and Division.
We use them to solve everyday problems involving numbers.
Addition, Subtraction, Multiplication and Division.
We use them to solve everyday problems involving numbers.
The four basic operations are addition, subtraction, multiplication and division.
We use them to solve problems in school, at home, in shops, on farms and in many jobs.
+ − × ÷
Operations help us calculate and solve problems.
By the end of this lesson, you should apply operations on whole numbers up to 10 000 and solve simple word problems.
The Four Operations
What does each operation mean?
+
Addition means putting together.
−
Subtraction means taking away or finding the difference.
×
Multiplication means repeated addition or groups of equal size.
÷
Division means sharing or grouping equally.
Activity: Which operation means sharing equally?
Addition
Subtraction
Multiplication
Division
Estimation
Estimating sums and differences
Estimation means finding an answer that is close to the exact answer.
We can round numbers before calculating.
Example: 3 984 + 2 106 is close to 4 000 + 2 000 = 6 000.
Example: 8 921 − 4 118 is close to 9 000 − 4 000 = 5 000.
Estimate: 4 876 + 3 021
About 5 000
About 8 000
About 12 000
Addition
Adding two or three numbers up to 10 000
Line up the digits according to place value.
Add ones, tens, hundreds and thousands carefully.
Example: 2 345 + 1 220 + 3 104 = 6 669.
Commutative Law of Addition: Changing the order does not change the sum.
4 + 7 = 7 + 4
4 + 7 = 7 + 4
Associative Law of Addition: Changing the grouping does not change the sum.
(3 + 5) + 2 = 3 + (5 + 2)
(3 + 5) + 2 = 3 + (5 + 2)
Identity Element of Addition: Adding zero does not change a number.
9 + 0 = 9
9 + 0 = 9
Calculate: 2 145 + 3 210 + 1 005
Subtraction
Subtracting whole numbers up to 10 000
Subtraction helps us find what remains or the difference between numbers.
Example: 9 850 − 4 325 = 5 525.
Always line up place values before subtracting.
Calculate: 8 764 − 3 421
Factors
Finding factors of numbers up to 50
A factor divides a number exactly with no remainder.
Factors of 12 are: 1, 2, 3, 4, 6, 12.
Factors are useful when finding HCF and LCM.
Tap all factors of 18.
1
2
3
4
6
9
18
LCM and HCF
Lowest Common Multiple and Highest Common Factor
LCM
The Lowest Common Multiple is the smallest number that is a multiple of two or more numbers.
Multiples of 4: 4, 8, 12, 16, 20
Multiples of 6: 6, 12, 18, 24
LCM of 4 and 6 is 12.
HCF
The Highest Common Factor is the greatest factor shared by two or more numbers.
Factors of 12: 1, 2, 3, 4, 6, 12
Factors of 18: 1, 2, 3, 6, 9, 18
HCF of 12 and 18 is 6.
What is the HCF of 8 and 12?
2
4
8
Multiplication
Multiplying whole numbers
Multiplication helps us calculate equal groups quickly.
Multiplying by 10 moves digits one place to the left: 45 × 10 = 450.
Multiplying by 100 moves digits two places to the left: 45 × 100 = 4 500.
Example: 234 × 12 = 2 808.
Calculate: 326 × 20
Division
Dividing whole numbers
Division helps us share or group numbers equally.
Example: 84 ÷ 7 = 12.
Sometimes there is a remainder. Example: 29 ÷ 4 = 7 remainder 1.
Calculate: 936 ÷ 9
Order of Operations
Solving number sentences up to 3 steps
Do multiplication and division before addition and subtraction.
Work from left to right when operations have the same importance.
Example: 6 + 4 × 3 = 6 + 12 = 18.
Do not calculate 6 + 4 first. Multiplication comes before addition.
Solve: 20 − 6 ÷ 2 + 3
10
20
17
Word Problems
Solving problems involving operations
Read the problem carefully.
Find the important numbers.
Choose the correct operation.
Calculate and check whether your answer makes sense.
Problem: A shopkeeper has 3 boxes. Each box has 125 pencils. How many pencils are there altogether?
128 pencils
375 pencils
250 pencils
Reflection: Write one occupation where people use number operations.
Final Quiz
Check your understanding
1. Estimate 3 920 + 2 080.
2. 5 + 0 = 5 shows the...
3. The HCF of 10 and 15 is...
4. 42 × 100 =
5. 5 + 3 × 4 =
Standard 5 Mathematics: Operations
Module 1: Numbers and Operation — Lesson 2: Addition, subtraction, multiplication, division, estimation, factors, LCM, HCF and order of operations.
Slide 1 / 12
Welcome ➕➖✖️➗
Today we learn how to apply the four basic operations on whole numbers
The four basic operations are:
Addition, Subtraction, Multiplication and Division.
We use them to solve everyday problems involving numbers.
Addition, Subtraction, Multiplication and Division.
We use them to solve everyday problems involving numbers.
The four basic operations are addition, subtraction, multiplication and division.
We use them to solve problems in school, at home, in shops, on farms and in many jobs.
+ − × ÷
Operations help us calculate and solve problems.
By the end of this lesson, you should apply operations on whole numbers up to 10 000 and solve simple word problems.
The Four Operations
What does each operation mean?
+
Addition means putting together.
−
Subtraction means taking away or finding the difference.
×
Multiplication means repeated addition or groups of equal size.
÷
Division means sharing or grouping equally.
Activity: Which operation means sharing equally?
Addition
Subtraction
Multiplication
Division
Estimation
Estimating sums and differences
Estimation means finding an answer that is close to the exact answer.
We can round numbers before calculating.
Example: 3 984 + 2 106 is close to 4 000 + 2 000 = 6 000.
Example: 8 921 − 4 118 is close to 9 000 − 4 000 = 5 000.
Estimate: 4 876 + 3 021
About 5 000
About 8 000
About 12 000
Addition
Adding two or three numbers up to 10 000
Line up the digits according to place value.
Add ones, tens, hundreds and thousands carefully.
Example: 2 345 + 1 220 + 3 104 = 6 669.
Commutative Law of Addition: Changing the order does not change the sum.
4 + 7 = 7 + 4
4 + 7 = 7 + 4
Associative Law of Addition: Changing the grouping does not change the sum.
(3 + 5) + 2 = 3 + (5 + 2)
(3 + 5) + 2 = 3 + (5 + 2)
Identity Element of Addition: Adding zero does not change a number.
9 + 0 = 9
9 + 0 = 9
Calculate: 2 145 + 3 210 + 1 005
Subtraction
Subtracting whole numbers up to 10 000
Subtraction helps us find what remains or the difference between numbers.
Example: 9 850 − 4 325 = 5 525.
Always line up place values before subtracting.
Calculate: 8 764 − 3 421
Factors
Finding factors of numbers up to 50
A factor divides a number exactly with no remainder.
Factors of 12 are: 1, 2, 3, 4, 6, 12.
Factors are useful when finding HCF and LCM.
Tap all factors of 18.
1
2
3
4
6
9
18
LCM and HCF
Lowest Common Multiple and Highest Common Factor
LCM
The Lowest Common Multiple is the smallest number that is a multiple of two or more numbers.
Multiples of 4: 4, 8, 12, 16, 20
Multiples of 6: 6, 12, 18, 24
LCM of 4 and 6 is 12.
HCF
The Highest Common Factor is the greatest factor shared by two or more numbers.
Factors of 12: 1, 2, 3, 4, 6, 12
Factors of 18: 1, 2, 3, 6, 9, 18
HCF of 12 and 18 is 6.
What is the HCF of 8 and 12?
2
4
8
Multiplication
Multiplying whole numbers
Multiplication helps us calculate equal groups quickly.
Multiplying by 10 moves digits one place to the left: 45 × 10 = 450.
Multiplying by 100 moves digits two places to the left: 45 × 100 = 4 500.
Example: 234 × 12 = 2 808.
Calculate: 326 × 20
Division
Dividing whole numbers
Division helps us share or group numbers equally.
Example: 84 ÷ 7 = 12.
Sometimes there is a remainder. Example: 29 ÷ 4 = 7 remainder 1.
Calculate: 936 ÷ 9
Order of Operations
Solving number sentences up to 3 steps
Do multiplication and division before addition and subtraction.
Work from left to right when operations have the same importance.
Example: 6 + 4 × 3 = 6 + 12 = 18.
Do not calculate 6 + 4 first. Multiplication comes before addition.
Solve: 20 − 6 ÷ 2 + 3
10
20
17
Word Problems
Solving problems involving operations
Read the problem carefully.
Find the important numbers.
Choose the correct operation.
Calculate and check whether your answer makes sense.
Problem: A shopkeeper has 3 boxes. Each box has 125 pencils. How many pencils are there altogether?
128 pencils
375 pencils
250 pencils
Reflection: Write one occupation where people use number operations.
Final Quiz
Check your understanding
1. Estimate 3 920 + 2 080.
2. 5 + 0 = 5 shows the...
3. The HCF of 10 and 15 is...
4. 42 × 100 =
5. 5 + 3 × 4 =
0
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