This is roughly School B's share (half of A). Solve the unit equation: 2u + u + (2u − 3 480) = 74 526, so 5u = 78 006, u = 15 601.20 — but this gives non-integer values. Re-check the constraint that A = 2B.
PRIMARY 3 · MATHEMATICS
Addition and Subtraction
Top 5 mistakes
Ranked by how often they appear across 21 MOE-aligned practice questions in our archive.
This is around (74 526 − 3 480) ÷ 3, treating the three schools as equal after one subtraction. School A is TWICE School B, not equal.
This is School A + 3 480, the value of School A's amount BEFORE accounting for School C's subtraction. Re-set up: B + 2B + (2B − 3 480) = 74 526.
Computed 320 − 175 = 145 cents correctly but added 10 extra cents through a units-place regrouping error, writing 155 cents = $1.55 instead of $1.45.
Misread $1.75 as $1.25 (confused the tens digit 7 with 2), then subtracted $3.20 − $1.25 = $1.95 instead of $3.20 − $1.75 = $1.45.
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