Advanced Mathematics Primary 5 Area of Triangle

ABCD is a rectangle with AB = 12 cm and BC = 8 cm. P is a point inside the rectangle such that the area of triangle APB is twice the area of triangle DPC. Find the area of triangle APB.

A 32 cm²
B 16 cm²
C 48 cm²
D 24 cm²
Show Worked Solution

Worked Solution

Step 1: Let h₁ be the perpendicular distance from P to AB, and h₂ be the perpendicular distance from P to DC. Since AB and DC are parallel sides of the rectangle, h₁ + h₂ = BC = 8 cm. Step 2: Area APB = ½ × 12 × h₁ = 6h₁. Area DPC = ½ × 12 × h₂ = 6h₂. Step 3: 'APB is twice DPC' gives 6h₁ = 2 × 6h₂, so h₁ = 2h₂. Step 4: From h₁ + h₂ = 8 and h₁ = 2h₂: 3h₂ = 8, so h₂ = 8/3, h₁ = 16/3. Step 5: Area APB = 6 × 16/3 = 32 cm². Answer: 32 cm²

Correct answer: 32 cm²

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