Advanced Mathematics Primary 5 Area of Triangle

A rectangular piece of cardboard ABCD is 18 cm long and 10 cm wide. A triangle is cut away from one corner of the rectangle. The triangle has a base of 12 cm along the bottom edge and a height of 10 cm (the full width of the rectangle). What is the area of the remaining shaded region?

A 60 cm²
B 120 cm²
C 150 cm²
D 180 cm²
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Worked Solution

Step 1: Find the area of the full rectangle. Area of rectangle = 18 × 10 = 180 cm² Step 2: Find the area of the triangle that was cut away. Area of triangle = ½ × base × height = ½ × 12 × 10 = 60 cm² Step 3: Subtract the triangle area from the rectangle area to get the shaded region. Shaded area = 180 − 60 = 120 cm² Answer: 120 cm² Answer: 120 cm²

Correct answer: 120 cm²

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