Highest common factor and lowest common multiple
Objective. Find HCF and LCM and apply them to scheduling problems.
- 1. Learn
- 2. Worked example
- 3. Practice
- 4. Feedback
- 5. Continue
Learn: the key idea
Highest common factor and lowest common multiple is built on a small number of dependable facts. Reveal number structure through divisibility and prime factorisation. Represent the information first, choose a method deliberately, show each step and use an inverse operation or estimate to check that the result fits the question.
Worked example
Find the LCM of 8 and 9.
- 1Identify the mathematical information and what must be found.
- 2Represent it with a number line, diagram, table or expression where helpful.
- 3Apply the relevant fact carefully and keep each line clear.
- 4Check the result against the conditions in the question: 72.
Answer: 72
Concept mastery
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Practice
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Start practisingCommon mistake. A common mistake in highest common factor and lowest common multiple is to apply a remembered procedure before reading the signs, units or order carefully. Write the structure first, then calculate and check.
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