Advanced Mathematics Primary 5 Area of Triangle

Triangle PQR is an obtuse triangle. QR = 14 cm is the base. Vertex P is positioned such that the perpendicular from P does not land inside the triangle — it falls on the extension of QR beyond R. The perpendicular distance from P to line QR (measured outside the triangle) is 6 cm. The slant side PQ measures 9 cm. What is the area of triangle PQR?

A 42 cm²
B 63 cm²
C 84 cm²
D 27 cm²
Show Worked Solution

Worked Solution

Step 1: Identify the base. Base = QR = 14 cm. Step 2: Identify the perpendicular height. For an obtuse triangle, the perpendicular from the opposite vertex may fall outside the triangle, on an extension of the base line. Here the perpendicular from P meets the extension of QR at 90°, and this perpendicular distance = 6 cm. This 6 cm is the correct height regardless of where the foot of the perpendicular lands. The slant side PQ = 9 cm is NOT the height. Step 3: Apply the area formula. Area of triangle PQR = ½ × base × height = ½ × 14 × 6 = 42 cm² Answer: 42 cm²

Correct answer: 42 cm²

Want more questions like this? Superholic Lab has 10,000+ MOE-aligned questions with full worked solutions.

Start Free Trial — 7 Days Free