Forgot to multiply by ½. Area of a triangle = ½ × base × height, not base × height.
PRIMARY 5 · MATHEMATICS
Area of Triangle
Top 5 mistakes
Ranked by how often they appear across 57 MOE-aligned practice questions in our archive.
You gave the area of triangle DPC (the smaller triangle), not triangle APB.
You assumed P sits at the midpoint between AB and DC, giving each triangle the same height of 4 cm: ½ × 12 × 4 = 24. The condition 'APB is twice DPC' means the heights split BC in a 2 : 1 ratio.
You gave half the rectangle area (96 ÷ 2). Triangles APB + DPC together cover only half the rectangle, but APB alone is 2/3 of that half = 32 cm² — not the whole half.
Computed the area of the cut-out triangle (½ × 8 × 6 = 24 cm²) and the area of the rectangle (12 × 8 = 96 cm²), then subtracted twice (96 − 24 − 24 = 48).
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