Mensuration 3D (Volume & Surface Area)

Master this topic with zero to advance depth.

1. Cube & Cuboid (рдШрди рдФрд░ рдШрдирд╛рдн)

Cuboid:

  • Volume: L├ЧB├ЧHL \times B \times H
  • Total Surface Area (TSA): 2(LB+BH+HL)2(LB + BH + HL)
  • Lateral Surface Area (LSA): 2(L+B)├ЧH2(L+B) \times H
  • Diagonal: L2+B2+H2\sqrt{L^2 + B^2 + H^2}
Cube:
  • Volume: a3a^3
  • TSA: 6a26a^2
  • LSA: 4a24a^2
  • Diagonal: a3a\sqrt{3}

Example:

Q: Find the volume of a cube with side 5 cm.
Solution: V=53=125┬аcm3V = 5^3 = 125 \text{ cm}^3.

2. Cylinder (рдмреЗрд▓рди)

Solid Cylinder:

  • Volume: ╧Аr2h\pi r^2 h
  • Curved Surface Area (CSA): 2╧Аrh2\pi rh
  • Total Surface Area (TSA): 2╧Аr(h+r)2\pi r(h+r)
Hollow Cylinder:
  • Volume: ╧Аh(R2тИТr2)\pi h(R^2 - r^2)
  • TSA: 2╧А(R+r)(h+RтИТr)2\pi(R+r)(h+R-r)

3. Cone (рд╢рдВрдХреБ)

Cone:

  • Slant Height (ll): h2+r2\sqrt{h^2 + r^2}
  • Volume: 13╧Аr2h\frac{1}{3} \pi r^2 h
  • Curved Surface Area (CSA): ╧Аrl\pi rl
  • Total Surface Area (TSA): ╧Аr(l+r)\pi r(l+r)

4. Sphere & Hemisphere (рдЧреЛрд▓рд╛ рдФрд░ рдЕрд░реНрдзрдЧреЛрд▓рд╛)

Sphere:

  • Volume: 43╧Аr3\frac{4}{3} \pi r^3
  • Surface Area: 4╧Аr24\pi r^2
Hemisphere:
  • Volume: 23╧Аr3\frac{2}{3} \pi r^3
  • Curved Surface Area (CSA): 2╧Аr22\pi r^2
  • Total Surface Area (TSA): 3╧Аr23\pi r^2

Example:

Q: Find the volume of a sphere with radius 3 cm.
Solution: V=43├Ч227├Ч33=43├Ч227├Ч27=36╧АтЙИ113.14V = \frac{4}{3} \times \frac{22}{7} \times 3^3 = \frac{4}{3} \times \frac{22}{7} \times 27 = 36\pi \approx 113.14.

5. Frustum of a Cone (рдЫрд┐рдиреНрдирдХ)

Volume: 13╧Аh(R2+r2+Rr)\frac{1}{3} \pi h (R^2 + r^2 + Rr)
CSA: ╧Аl(R+r)\pi l (R+r) where l=h2+(RтИТr)2l = \sqrt{h^2 + (R-r)^2}
TSA: ╧Аl(R+r)+╧АR2+╧Аr2\pi l (R+r) + \pi R^2 + \pi r^2