Advanced Mathematics Primary 5 Area of Triangle

Triangle PQR is drawn on a square grid where each grid unit represents 1 cm. P and Q lie on the same horizontal gridline and PQ = 6 cm. R is located 2 cm to the right of P and 3 cm directly above the line PQ. The slant side QR measures 5 cm. What is the area of triangle PQR?

A 9 cm²
B 12 cm²
C 15 cm²
D 18 cm²
Show Worked Solution

Worked Solution

Step 1: Identify the base and perpendicular height. Base PQ = 6 cm (lies along the horizontal gridline). Step 2: The height must be perpendicular to the base. R is 3 cm directly above line PQ, so the perpendicular height = 3 cm. (QR = 5 cm is a slant side — it is not perpendicular to PQ.) Step 3: Area = ½ × base × height = ½ × 6 × 3 = 9 cm²

Correct answer: 9 cm²

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