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Stage 9 Mathematics — Complete Revision Notes

The last year before IGCSE: every Stage 9 topic with definitions, worked examples shown step by step, the mistakes students actually make, and English–Thai key terms.

Cambridge Lower Secondary — Stage 9 · Equivalent to ม.3 / Grade 9 · 11 chapters · ~116 min to read

Contents

  1. 1

    Indices, Surds and Standard Form

    Indices, Surds and Standard Formin review

    Index laws extended to fractional powers, which turns every root into a power — and the surd arithmetic that keeps answers exact instead of rounded.

    3 sections·~10 min·จำนวนและพีชคณิต (Number and Algebra)·CC 8.EE, N-RN

  2. 2

    Rounding, Bounds and Accuracy

    Rounding, Bounds and Accuracyin review

    What a rounded measurement actually tells you — and why every measured number is a range rather than a value, which changes what you may claim about a calculation.

    3 sections·~10 min·จำนวนและพีชคณิต (Number and Algebra)·CC N-Q, 7.NS

  3. 3

    Percentages and Compound Change

    Percentages and Compound Changein review

    Repeated percentage change — interest, depreciation and population growth — and the reverse question that asks what something was worth before.

    3 sections·~10 min·จำนวนและพีชคณิต (Number and Algebra)·CC 7.RP, F-LE

  4. 4

    Direct and Inverse Proportion

    Direct and Inverse Proportionin review

    Proportion written as an equation rather than worked as a recipe — which is what lets you answer questions the unitary method cannot reach.

    3 sections·~9 min·จำนวนและพีชคณิต (Number and Algebra)·CC 7.RP, 8.F

  5. 5

    Quadratic Expressions and Equations

    Quadratic Expressions and Equationsin review

    Factorising a quadratic and using it to solve — the first equations in this book with two answers, and the property that makes finding them possible.

    3 sections·~11 min·จำนวนและพีชคณิต (Number and Algebra)·CC A-SSE, A-REI

  6. 6

    Simultaneous Equations

    Simultaneous Equationsin review

    Two equations, two unknowns, and three ways to find the pair that satisfies both — plus what it means when there is no such pair.

    3 sections·~11 min·จำนวนและพีชคณิต (Number and Algebra)·CC 8.EE, A-REI

  7. 7

    Linear, Quadratic and Real-Life Graphs

    Linear, Quadratic and Real-Life Graphsin review

    Reading a straight line from its equation, sketching a parabola from its factors, and interpreting the graphs that describe journeys.

    3 sections·~10 min·จำนวนและพีชคณิต (Number and Algebra)·CC 8.F, F-IF

  8. 8

    Similarity and Congruence

    Similarity and Congruencein review

    Same shape against same shape and size — and the scale factors for length, area and volume, which are three different numbers and the reason most of these questions are got wrong.

    3 sections·~10 min·การวัดและเรขาคณิต (Geometry and Measure)·CC 8.G, G-SRT

  9. 9

    Trigonometry

    Trigonometryin review

    Connecting an angle to the sides of a right-angled triangle — which makes heights and distances you cannot reach into things you can calculate.

    3 sections·~12 min·การวัดและเรขาคณิต (Geometry and Measure)·CC G-SRT

  10. 10

    Circles, Prisms and Solids

    Circles, Prisms and Solidsin review

    Arcs and sectors as fractions of a circle, and the volumes and surface areas of the solids built from circles and polygons.

    3 sections·~10 min·การวัดและเรขาคณิต (Geometry and Measure)·CC 7.G, G-GMD

  11. 11

    Statistics and Probability

    Statistics and Probabilityin review

    Averages from grouped data, scatter graphs and what correlation does not prove, and the probability of two events happening together.

    3 sections·~13 min·สถิติและความน่าจะเป็น (Statistics and Probability)·CC S-ID, S-CP, 8.SP

Which curricula this maps to

Chapter order follows the Cambridge syllabus this book is written for. Each chapter also states its US Common Core domains and the matching สสวท. strand, so a student moving between an international programme and the Thai system can see where the same ground sits in the other curriculum.

Note: we name strands and domains, never individual indicator codes. Mapping to a single indicator requires interpretation, and we would rather not claim precision we cannot defend.

MathPrepAI is not affiliated with, endorsed by, or connected to Cambridge Assessment International Education. Syllabus names and codes are used only to say what this book covers. Every problem here is written for this book rather than taken from a past paper.