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Topic 2 of 8 · Grade 7

Operations on whole numbers

Addition, subtraction, multiplication and division, including long multiplication and long division.

Notes for this topic 1 file, in order

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  1. PDFOperations on whole numbers – Mathematics notes (ZIMSEC Primary)47.5 KB

The four operations

Addition, subtraction, multiplication and division, including long multiplication and long division.

Worked example: Calculate 348 × 26.

348 × 20 = 6 960; 348 × 6 = 2 088; total = 9 048

Worked example: Calculate 1 575 ÷ 15.

1 575 ÷ 15 = 105

Order of operations (BODMAS)

Brackets, Orders (powers), Division and Multiplication (left to right), Addition and Subtraction (left to right).

Worked example: Work out 20 − 3 × (4 + 2).

Brackets first: 4 + 2 = 6; then 3 × 6 = 18; then 20 − 18 = 2

Factors, multiples and primes

  • Factors of 12: 1, 2, 3, 4, 6, 12.
  • Multiples of 4: 4, 8, 12, 16, …
  • A prime number has exactly two factors: 2, 3, 5, 7, 11, 13, …
  • HCF (highest common factor) and LCM (lowest common multiple).

Worked example: Find the HCF and LCM of 12 and 18.

Factors of 12: 1, 2, 3, 4, 6, 12; factors of 18: 1, 2, 3, 6, 9, 18 → HCF = 6

Multiples: 12, 24, 36…; 18, 36… → LCM = 36

Squares and square roots

7² = 49; √81 = 9.

Exam tip: Always check division answers by multiplying back.

Check yourself

  1. Work out 5 + 4 × 3.
  2. List the prime numbers between 10 and 20.
  3. Find the LCM of 6 and 8.
Show answers
  1. 17
  2. 11, 13, 17, 19
  3. 24
Next topicFractions, decimals and percentages

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