Surface Area and Volume of Cuboids and Prisms
A cuboid is a three-dimensional rectangular box shape with six rectangular faces. It has 8 vertices and 12 edges in total. This section covers the formulas and calculations for the volume of cuboid and its surface area.
Definition: A cuboid is a box-shaped object with six rectangular faces.
The volume of a cuboid is calculated using the formula:
Volume = length × width × height (V = l × w × h)
Example: For a cuboid with dimensions 6 cm × 4 cm × 3.5 cm, the volume is:
V = 6 × 4 × 3.5 = 84 cm³
The surface area of a cuboid is found by calculating the total area of all six rectangular faces. The formula is:
Surface Area = 2(lw + lh + wh)
Example: For the same cuboid, the surface area is:
SA = 2(6×4 + 6×3.5 + 4×3.5) = 118 cm²
Highlight: Remember that opposite faces of a cuboid have the same area, which simplifies the surface area calculation.
The concept of prisms is introduced, which are three-dimensional shapes with a constant cross-section throughout their length.
Definition: A prism is a 3D shape with the same cross-section running all the way through it.
The volume of a prism is calculated by multiplying the area of its cross-section by the length of the prism:
Volume of prism = Area of cross-section × Length
Example: For a triangular prism with base 6 cm, height 8 cm, and length 9 cm:
Volume = (1/2 × 6 × 8) × 9 = 216 cm³
Surface Area = 2(1/2 × 6 × 8) + (6 × 9) + (8 × 9) + (10 × 9) = 282 cm²