The real-number map
Natural numbers sit inside whole numbers, which sit inside integers, rational numbers and finally the real numbers.
CSEC Math LabLearn · practise · master
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All sections
12 min
Section 1Number Theory and Computation
Know what kind of number you are dealing with
Distinguish number sets and use factors, multiples and number properties to solve problems.
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Learn the idea
Three things to notice
Rational means expressible as a fraction
Every terminating or recurring decimal is rational. Non-terminating, non-recurring decimals such as √2 are irrational.
Prime factors reveal structure
A prime-factor tree makes the HCF, LCM, square roots and divisibility easier to see.
Do not memorise the words alone. The worked example shows how to choose and apply the idea.
Syllabus coverage
Number setsFractions, decimals and percentagesHCF and LCMRatio and proportionSequencesApproximation