Surface Areas and Volumes

Class 10 Maths - Chapter 12 | NCERT Formula Sheet

1. Cube

Surface Area

• Total Surface Area = 6a²
• Lateral Surface Area = 4a²

Volume

Volume = a³

Diagonal

Face diagonal = av2
Space diagonal = av3

2. Cuboid

Surface Area

• TSA = 2(lb + bh + hl)
• LSA = 2h(l + b)

Volume

Volume = l × b × h

Diagonal

Diagonal = v(l² + b² + h²)

3. Right Circular Cylinder

Surface Area

• TSA = 2pr(h + r)
• CSA = 2prh

Volume

Volume = pr²h

Hollow Cylinder

Volume = ph(R² - r²)
TSA = 2ph(R + r) + 2p(R² - r²)

4. Right Circular Cone

Surface Area

• TSA = pr(l + r)
• CSA = prl
• l = v(h² + r²)

Volume

Volume = (1/3)pr²h

Slant Height

l = v(h² + r²)
h = v(l² - r²)

5. Sphere and Hemisphere

Shape Surface Area Volume
Sphere 4pr² (4/3)pr³
Hemisphere (Solid) 3pr² (2/3)pr³
Hemisphere (Hollow) 2pr² (2/3)pr³

6. Frustum of a Cone

• Slant height: l = v[h² + (R - r)²]
• CSA = pl(R + r)
• TSA = pl(R + r) + p(R² + r²)
• Volume = (1/3)ph(R² + r² + Rr)

7. Combination of Solids

General Approach:

  1. Identify individual solids in combination
  2. Calculate surface area/volume of each
  3. Add for total volume
  4. For surface area: Subtract common areas where joined

8. Common Combinations

Cone on Cylinder

Total height = h1 + h2
Volume = pr²h1 + (1/3)pr²h2

Hemisphere on Cylinder

Total height = r + h
Volume = pr²h + (2/3)pr³

Cone on Hemisphere

Same radius r
Volume = (2/3)pr³ + (1/3)pr²h

9. Conversion of Solids

Important Principle: Volume remains constant when solid is melted and recast into different shape.
If solid A is melted to form solid B:
Volume of A = Volume of B
Number of smaller solids = Volume of bigger solid ÷ Volume of smaller solid

10. Quick Reference Table

Solid Volume TSA
Cube (side a) 6a²
Cuboid (l,b,h) lbh 2(lb+bh+hl)
Cylinder (r,h) pr²h 2pr(h+r)
Cone (r,h) (1/3)pr²h pr(l+r)
Sphere (r) (4/3)pr³ 4pr²
Hemisphere (r) (2/3)pr³ 3pr²

11. Example Problems (NCERT Style)

Problem 1: A cone of height 24 cm and radius 6 cm is made. Find its volume and curved surface area.

Solution:
Volume = (1/3)pr²h = (1/3) × (22/7) × 6² × 24
= (1/3) × (22/7) × 36 × 24 = (22 × 36 × 8)/7 = 6336/7 ˜ 905.14 cm³

Slant height l = v(h² + r²) = v(576 + 36) = v612 = 6v17 cm
CSA = prl = (22/7) × 6 × 6v17 ˜ 132v17/7 cm²
Problem 2: A hemispherical bowl of internal diameter 36 cm contains liquid. This liquid is to be filled into cylindrical bottles of radius 3 cm and height 6 cm. How many bottles are needed?

Solution:
Radius of hemisphere = 18 cm
Volume of hemisphere = (2/3)pr³ = (2/3) × p × 18³ = 3888p cm³
Volume of one bottle = pr²h = p × 3² × 6 = 54p cm³
Number of bottles = 3888p ÷ 54p = 72 bottles
Problem 3: A cuboidal water tank is 6 m long, 5 m wide and 4.5 m deep. How many liters of water can it hold?

Solution:
Volume = l × b × h = 6 × 5 × 4.5 = 135 m³
1 m³ = 1000 liters
Capacity = 135 × 1000 = 135,000 liters

12. Important Points to Remember

13. Conversion Units

• 1 cm³ = 1 mL
• 1 liter = 1000 cm³ = 1000 mL
• 1 m³ = 1000 liters = 106 cm³
• 1 km = 1000 m, 1 m = 100 cm
• 1 hectare = 10000 m²