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Lessons by Mr Chan
Mr Chan leads Number and Algebra classes in a Kowloon secondary school. He writes clear notes on directed numbers, estimation and exam pacing for Secondary 2–3.
Directed numbers: add, subtract, multiply and divideUse number-line sense and sign rules so directed-number calculations stay accurate under exam pressure.Numbers & Estimation· Mr ChanMCQ2
Approximate values and sensible estimationRound to a required accuracy, estimate products and quotients, and check whether an answer is reasonable.Numbers & Estimation· Mr ChanMCQ3
Prime factorisation, HCF and LCMWrite numbers as products of primes, then read off HCF and LCM — a frequent TSA-style opener.Numbers & Estimation· Mr ChanMCQ4
Scientific notation and large/small numbersConvert between ordinary form and a × 10ⁿ with 1 ≤ |a| < 10 — standard S3 index work.Numbers & Estimation· Mr ChanMCQ5
Mixed Number & Algebra drill (TSA style)A timed-style mixed set: primes, percentage change, expansion, factorisation and a linear equation.Exam & Challenge· Mr ChanMCQ6
Ordering directed numbers on the number lineCompare and arrange positive and negative integers for S2 foundation checks.Numbers & Estimation· Mr ChanMCQ7
Converting fractions and decimalsMove fluently between fractions, terminating decimals and recurring decimals.Numbers & Estimation· Mr ChanMCQ8
Finding a percentage of a quantityConvert percentages to multipliers and find parts of amounts quickly.Percentage, Rate & Ratio· Mr ChanMCQ9
Simple interest: finding P, R or TRearrange I = PRT/100 to find missing principal, rate or time.Percentage, Rate & Ratio· Mr ChanMCQ10
Substituting values into algebraic expressionsReplace letters carefully with brackets, especially for negatives.Algebraic Manipulation· Mr ChanMCQ11
Recognising a³ − b³ patterns (intro)Spot cubes and quote a³ − b³ = (a−b)(a²+ab+b²) at junior challenge level.Algebraic Manipulation· Mr ChanMCQ12
Simplifying simple algebraic fractionsCancel common factors only — never cancel terms across a plus sign.Algebraic Manipulation· Mr ChanMCQ13
Elimination with multiplied equationsScale both equations so one variable cancels cleanly.Equations & Inequalities· Mr ChanMCQ14
Changing subject when the formula has fractionsClear denominators before isolating the new subject.Equations & Inequalities· Mr ChanMCQ15
Exam mix: ratio and proportionShare ratios and decide direct versus inverse proportion quickly.Exam & Challenge· Mr ChanMCQ