Maths · Number. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
This topic is the base of all number work: putting numbers in order, calculating with them, and breaking whole numbers into primes.
To compare fractions, decimals and negatives, change them all to decimals. For negative numbers, the one further left on the number line is smaller, so −0.3 is less than −0.25. In a calculation, follow the order of operations, not the order you read it.
Every whole number above 1 can be written as a product of prime factors in only one way. That product gives you the HCF and LCM quickly. To count combinations, multiply the number of choices at each stage (the product rule).
Working from left to right and ignoring priority, for example writing 10 − 2 × 3 = 24. Multiplication comes before subtraction, so it is 10 − 6 = 4.
Answer: HCF = 12, LCM = 840
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