Geometry & Mensuration – Complete Concept Guide for CHSL 2026

Master Geometry & Mensuration with this comprehensive study guide designed specifically for CHSL aspirants. This guide covers key concepts, shortcuts, and includes 10 practice MCQs to test your understanding.

Geometry & Mensuration – Key Formulas

Mensuration questions appear in almost every exam. Mastering area, perimeter, volume, and surface area formulas is essential.

2D Figures

ShapeAreaPerimeter
Rectanglel × b2(l+b)
Square4a
Triangle½ × b × ha+b+c
Circleπr²2πr
Trapezium½(a+b)ha+b+c+d
Rhombus½×d1×d24a

3D Figures

ShapeVolumeSurface Area
Cube6a²
Cuboidl×b×h2(lb+bh+lh)
Cylinderπr²h2πr(r+h)
Sphere4/3 πr³4πr²
Cone1/3 πr²hπr(r+l) where l=slant height

Shortcuts

  • Pythagoras: a² + b² = c² (Common triples: 3-4-5, 5-12-13, 8-15-17)
  • Equilateral triangle area = (√3/4)a²
  • Area of rhombus = (d1 × d2)/2; always remember both diagonals

Practice MCQs: Geometry & Mensuration

Test your understanding with these 10 targeted MCQs based on the concepts above.

Q1. The area of a circle with radius 7 cm is: (π = 22/7)

  • A. 154 cm²
  • B. 144 cm²
  • C. 164 cm²
  • D. 174 cm²

Correct Answer: A

Area = πr² = (22/7) × 7 × 7 = 22 × 7 = 154 cm².

Q2. Find the volume of a cube with side 5 cm.

  • A. 100 cm³
  • B. 115 cm³
  • C. 125 cm³
  • D. 135 cm³

Correct Answer: C

Volume of cube = a³ = 5³ = 5 × 5 × 5 = 125 cm³.

Q3. The perimeter of a rectangle is 56 cm. If the length is 18 cm, find the breadth.

  • A. 8 cm
  • B. 10 cm
  • C. 12 cm
  • D. 14 cm

Correct Answer: B

Perimeter = 2(l+b). 56 = 2(18+b). 28 = 18+b. b = 10 cm.

Q4. A right triangle has legs 6 cm and 8 cm. Find the hypotenuse.

  • A. 9 cm
  • B. 10 cm
  • C. 11 cm
  • D. 12 cm

Correct Answer: B

Using Pythagoras: c² = 6² + 8² = 36 + 64 = 100. c = 10 cm. (This is a 6-8-10 = 3-4-5 triple × 2)

Q5. The area of an equilateral triangle with side 4 cm is:

  • A. 4√3 cm²
  • B. 6√3 cm²
  • C. 8√3 cm²
  • D. 12√3 cm²

Correct Answer: A

Area = (√3/4) × a² = (√3/4) × 16 = 4√3 cm².

Q6. Volume of a cylinder with radius 7 cm and height 10 cm is:

  • A. 1440 cm³
  • B. 1540 cm³
  • C. 1640 cm³
  • D. 1740 cm³

Correct Answer: B

V = πr²h = (22/7) × 7² × 10 = (22/7) × 49 × 10 = 22 × 7 × 10 = 1540 cm³.

Q7. The diagonal of a square is 10√2 cm. What is its area?

  • A. 50 cm²
  • B. 100 cm²
  • C. 150 cm²
  • D. 200 cm²

Correct Answer: B

Diagonal of square = a√2. So a√2 = 10√2, a = 10 cm. Area = a² = 100 cm².

Q8. A rhombus has diagonals 12 cm and 16 cm. Find its area.

  • A. 72 cm²
  • B. 84 cm²
  • C. 96 cm²
  • D. 108 cm²

Correct Answer: C

Area of rhombus = (d1 × d2)/2 = (12 × 16)/2 = 192/2 = 96 cm².

Q9. Total surface area of a sphere with radius 3.5 cm is: (π = 22/7)

  • A. 154 cm²
  • B. 164 cm²
  • C. 174 cm²
  • D. 184 cm²

Correct Answer: A

TSA = 4πr² = 4 × (22/7) × (3.5)² = 4 × (22/7) × 12.25 = 4 × 38.5 = 154 cm².

Q10. The volume of a cone with radius 6 cm and height 7 cm is: (π = 22/7)

  • A. 264 cm³
  • B. 274 cm³
  • C. 284 cm³
  • D. 294 cm³

Correct Answer: A

V = (1/3)πr²h = (1/3) × (22/7) × 36 × 7 = (1/3) × 22 × 36 = 22 × 12 = 264 cm³.