1
The sum of the interior angles of a triangle is:
Correct answer: D. 180°
The three angles of any triangle add up to 180°.
easy
Geometry and Mensuration MCQs
Solved Mathematics MCQs on angles, triangles and polygons, area and perimeter, circles, and volume and surface area of solids, with worked solutions.
20 MCQsUpdated 27 October 2026
This set covers angles and polygons, and the areas, perimeters and volumes of everyday shapes: triangles, rectangles, circles, cubes and cylinders.
Write down the formula before substituting numbers; most mistakes in mensuration come from mixing up area and perimeter or radius and diameter. Unless told otherwise, use π = 22/7 when the radius is a multiple of 7.
- 2
Two angles of a triangle are 65° and 45°. What is the third angle?
Correct answer: C. 70°
Third angle = 180° − 65° − 45° = 70°.
easy - 3
What is the sum of the interior angles of a hexagon (6 sides)?
Correct answer: C. 720°
Sum = (n − 2) × 180° = (6 − 2) × 180° = 720°.
medium - 4
Each exterior angle of a regular octagon (8 sides) measures:
Correct answer: C. 45°
Exterior angles of any polygon add up to 360°, so each is 360° ÷ 8 = 45°.
hard - 5
An angle greater than 90° but less than 180° is called:
Correct answer: B. Obtuse
Acute is less than 90°, right is exactly 90°, obtuse is between 90° and 180°, and reflex is between 180° and 360°.
easy - 6
Two angles whose sum is 90° are called:
Correct answer: B. Complementary angles
Complementary angles add up to 90°. Supplementary angles add up to 180°.
easy - 7
What is the area of a rectangle 12 m long and 8 m wide?
Correct answer: D. 96 m²
Area = length × width = 12 × 8 = 96 m².
easy - 8
What is the perimeter of a rectangle 15 cm long and 10 cm wide?
Correct answer: A. 50 cm
Perimeter = 2 × (length + width) = 2 × (15 + 10) = 50 cm.
easy - 9
What is the area of a triangle with base 10 cm and height 6 cm?
Correct answer: B. 30 cm²
Area = ½ × base × height = ½ × 10 × 6 = 30 cm².
easy - 10
What is the area of a circle of radius 7 cm? (Take π = 22/7)
Correct answer: C. 154 cm²
Area = πr² = 22/7 × 7 × 7 = 154 cm².
medium - 11
What is the circumference of a circle of radius 14 cm? (Take π = 22/7)
Correct answer: C. 88 cm
Circumference = 2πr = 2 × 22/7 × 14 = 88 cm.
medium - 12
The two shorter sides of a right-angled triangle are 6 cm and 8 cm. What is the hypotenuse?
Correct answer: A. 10 cm
By Pythagoras: √(6² + 8²) = √(36 + 64) = √100 = 10 cm.
medium - 13
What is the volume of a cube with side 5 cm?
Correct answer: D. 125 cm³
Volume = side³ = 5 × 5 × 5 = 125 cm³.
easy - 14
What is the total surface area of a cube with side 4 cm?
Correct answer: B. 96 cm²
A cube has 6 square faces: 6 × 4² = 6 × 16 = 96 cm².
medium - 15
What is the volume of a box (cuboid) 10 cm × 6 cm × 4 cm?
Correct answer: A. 240 cm³
Volume = length × width × height = 10 × 6 × 4 = 240 cm³.
easy - 16
What is the volume of a cylinder with radius 7 cm and height 10 cm? (Take π = 22/7)
Correct answer: B. 1,540 cm³
Volume = πr²h = 22/7 × 7 × 7 × 10 = 1,540 cm³.
hard - 17
A square has a perimeter of 56 cm. What is its area?
Correct answer: B. 196 cm²
Side = 56 ÷ 4 = 14 cm. Area = 14 × 14 = 196 cm².
medium - 18
The diagonals of a rhombus are 12 cm and 16 cm. What is its area?
Correct answer: D. 96 cm²
Area of a rhombus = ½ × d₁ × d₂ = ½ × 12 × 16 = 96 cm².
hard - 19
A polygon with 5 sides is called a:
Correct answer: A. Pentagon
Penta- means five. A hexagon has 6 sides, a heptagon 7 and an octagon 8.
easy - 20
If the radius of a circle is 25 cm, its diameter is:
Correct answer: A. 50 cm
Diameter = 2 × radius = 50 cm.
easy