Number

Addition, Subtraction, Multiplication, Division

3rd Class · 4th Class · 5th Class · 6th Class

  • By the end of this lesson students will be able to perform long multiplication with multi-digit numbers.
  • By the end of this lesson students will be able to perform long division with multi-digit numbers, including remainders.
  • By the end of this lesson students will be able to apply the correct order of operations (BODMAS) to solve mathematical problems.
  • By the end of this lesson students will be able to solve multi-step problems involving all four basic operations.

Key concepts

Long Multiplication

Long multiplication is a method used to multiply multi-digit numbers. It breaks down the multiplication into smaller, manageable steps using place value. You multiply each digit of the bottom number by each digit of the top number, starting from the right. Remember to carry over tens and to add a zero as a placeholder when multiplying by the tens digit (or hundreds digit, and so on). Finally, you add all the partial products together to get the final answer.

Long Division

Long division is a method for dividing large numbers into smaller groups or parts. It involves a series of steps: Divide, Multiply, Subtract, Bring Down. You start by dividing the first digit (or first few digits) of the dividend by the divisor. Write the quotient above. Multiply the quotient by the divisor and write the product below the part of the dividend you just divided. Subtract this product. Bring down the next digit of the dividend and repeat the process until there are no more digits to bring down. Any number left at the end is the remainder.

Order of Operations (BODMAS)

When a maths problem has more than one operation (like addition, subtraction, multiplication, or division), we need a special order to solve it to make sure everyone gets the same answer. This order is called BODMAS: B - Brackets first. Solve anything inside brackets ( ) before anything else. O - Orders (or 'Of'). This refers to powers or indices, but for primary school, it's often simplified or not included. D - Division. Do any division next. M - Multiplication. Do any multiplication next. (Note: Division and Multiplication have the same priority. You do them from left to right as they appear in the problem.) A - Addition. Do any addition next. S - Subtraction. Do any subtraction last. (Note: Addition and Subtraction have the same priority. You do them from left to right as they appear in the problem.)

Key facts to remember

  • 1BODMAS stands for Brackets, Orders, Division/Multiplication, Addition/Subtraction.
  • 2Division and multiplication have equal priority; perform them from left to right.
  • 3Addition and subtraction have equal priority; perform them from left to right.
  • 4Place value is essential for correctly performing long multiplication and long division.
  • 5Multiplication and division are inverse operations (they 'undo' each other).
  • 6Addition and subtraction are inverse operations (they 'undo' each other).
  • 7Any number multiplied by zero is zero.
  • 8Any number divided by one is the number itself.

Worked examples

Example 1

Multiply 345 by 23.

IStep 1: Multiply 345 by the units digit of 23, which is 3.
II 345
III x 23
IV -----
V 1035 (345 x 3)
VIStep 2: Multiply 345 by the tens digit of 23, which is 2 (or 20). Remember to put a zero as a placeholder in the units column.
VII 345
VIII x 23
9 -----
10 1035
11 6900 (345 x 20)
12Step 3: Add the two partial products.
13 1035
14+ 6900
15 ------
16 7935

Answer

7935

Always align your numbers carefully according to their place value.

Example 2

Divide 876 by 12.

IStep 1: Can 12 go into 8? No. So, consider the first two digits, 87.
IIStep 2: How many times does 12 go into 87? We can estimate: 12 x 7 = 84, 12 x 8 = 96. So, 12 goes into 87 seven times.
III 7
IV12|876
V -84
VI ---
VII 3
VIIIStep 3: Subtract 84 from 87, which leaves 3.
9Step 4: Bring down the next digit, 6, to make 36.
10 7
1112|876
12 -84
13 ---
14 36
15Step 5: How many times does 12 go into 36? 12 x 3 = 36. So, 12 goes into 36 three times.
16 73
1712|876
18 -84
19 ---
20 36
21 -36
22 ---
23 0
24Step 6: Subtract 36 from 36, which leaves 0. There are no more digits to bring down, and the remainder is 0.

Answer

73

Knowing your multiplication tables well makes long division much easier and faster.

Example 3

Solve: (15 - 3) × 4 + 10 ÷ 2

IStep 1: Do the operation inside the Brackets first.
II (15 - 3) × 4 + 10 ÷ 2
III = 12 × 4 + 10 ÷ 2
IVStep 2: Next, do Multiplication and Division from left to right. First, the multiplication.
V = 12 × 4 + 10 ÷ 2
VI = 48 + 10 ÷ 2
VIIStep 3: Now, the division.
VIII = 48 + 10 ÷ 2
9 = 48 + 5
10Step 4: Finally, do the Addition.
11 = 48 + 5
12 = 53

Answer

53

Remember that multiplication and division have equal priority, and you work from left to right. The same applies to addition and subtraction.

Common mistakes

  • Forgetting to add a zero placeholder when multiplying by the tens digit (or higher place values) in long multiplication.
  • Misaligning digits when adding partial products in long multiplication or when subtracting in long division.
  • Not following the correct order of operations (BODMAS), especially doing addition/subtraction before multiplication/division.
  • Making errors with basic multiplication tables, which impacts accuracy in long multiplication and division.
  • Incorrectly handling remainders in division problems.

Exam tips

  • Always show all your working steps clearly, especially for long multiplication and division, as this can earn you partial marks.
  • Practise your multiplication tables regularly until you know them by heart – this will speed up your calculations and reduce errors.
  • After solving a problem, especially with long division, check your answer using the inverse operation (e.g., multiply your quotient by the divisor, then add the remainder, to see if you get the original dividend).
  • When using BODMAS, write out each step on a new line to keep your work tidy and easy to follow.

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