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第 22 週 · 應試銜接 · 第 2 節

P1 甲部(1) 九題位逐位攻略

35 分保底工程！DSE 卷一甲部(1) 共 9 題 35 分，題位 13 年不變、全港正確率最高 —— 每個題位一套<u>標準模板</u>，目標 <strong>25 分鐘拿滿</strong>，把時間留給乙部。

Paper 1 Section A(1): 9 slots, 35 marksQ1 indices (3)simplify powersQ2 subject (3)rearrange formulaQ3 factorize (3)4-move treeQ4 interest (4)compound + approxQ5 percent (4)cost-mark-sellQ6 inequal. (4)and/or + integerQ7 ratio (4)let k methodQ8 angles (5)circle / triangleQ9 stats (5)freq table + probtarget: 35/35 in 25 min3 min per slot, skip if stucksame 9 slots for 13 years
▶ 第一關： Q1–Q3 代數化簡三連（9 分）
factorization: 4-move decision tree1. common factor?take it out first, alwayscount the terms left2 terms3 terms4 terms2. diff. of squaresa2-b2=(a+b)(a-b)3. perfect squareor cross methodax2+bx+c4. grouping2+2 pairsDSE pattern: part (a) result isthe stepping stone for part (b)ask the 4 questions in this exact order
cross method: 2x2 + 7x + 32xx13split 2x2split 3check middle: 2x×3 + x×1 = 7x ✓read across: (2x + 1)(x + 3)if the check fails, swap or re-sign the right column
▶ 第二關： Q4–Q6 數字應用三連（12 分）
percent chain: cost to profitcost$400marked$640selling$512x (1+60%)x 0.8profit = selling - cost = $112profit% = profit / COST x 100% = 28%reverse question: let marked price = $x, solve one equation
AND = overlap / OR = unionx ≤ 2 AND x > -2-2 (open)2 (closed)overlap: -2 < x ≤ 2x ≤ 2 OR x > 4 : keep BOTH pieces24closed dot = included, open dot = excluded
▶ 第三關： Q7–Q9 幾何統計三連（14 分）
angle chase: mark, relate, sumOABC100504040OA = OB (radii)isos.: base 40 eachat centre = 2xat circum. = 50(180 - 100) / 2 = 40 ; 100 / 2 = 50
Q9 frequency table: solve x firstmark1234freq3x62mean = 2.5 : (29 + 2x)/(11 + x) = 2.5 so x = 3cumulative freq: 3, 6, 12, 14 (total 14)median position = 7th and 8th, both in mark 3mode = 3 (freq 6) ; P(mark ≥ 3) = 8/14 = 4/7always substitute x back before finding median
⚔ BOSS： 九題位全跑計時賽（25 分鐘 35 分）
pacing: 3 min per slot, 27 min capQ1-Q3 : 6-7 minQ4-Q6 : 9 minQ7-Q9 : 9-10 min071626 minstuck over 3 min? SKIP, mark it,come back after Q935 marks banked = time saved for Section Bcheck the minus signs before moving on