Royal College, Colombo 07 Grade 11 Maths Term 3 Test 2020

Customs duty as a percentage of value

Answer: 8%

💡 What it's asking: We know the duty paid and the item's value, and want the duty as a percentage. Percentage = part ÷ whole × 100.

1. 1The part is the duty, Rs. 720; the whole is the value, Rs. 9000.
2. 2Divide: 720 ÷ 9000 = 0.08.
3. 3Multiply by 100: 0.08 × 100 = 8%.

✅ 8% of 9000 = 9000 × 8/100 = 720, the duty given.

Angle using an isosceles triangle and exterior angle

Answer: 30 degrees

💡 What it's asking: Look for the equal-length marks: they make a small isosceles triangle. Its equal angles and the exterior-angle rule give you an angle in the left triangle, and then x.

1. 1The marks show the line from the top equals the right part of the base, so the small right-hand triangle is isosceles.
2. 2Its angle at the right corner equals the 40° at the top: 40°.
3. 3The exterior angle of that triangle at the foot of the line is 40° + 40° = 80°. This is an angle of the left triangle.
4. 4In the left triangle: x = 180° − 70° − 80° = 30°.

✅ The left triangle's angles 70°, 80° and 30° add to 180°.

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