The surface area or the total surface area of a cube is the entire space occupied by its outer faces. In other words, it is the number of unit squares needed to cover its shape. It is expressed in square units such as m2, cm2, mm2, or in2.
Formula
The formula is:
Surface Area of a Cube
How to Find the Surface Area of a Cube
Let us understand how we consider the faces of a cube and calculate its surface area with a help of a net.
How to Find the Surface Area of a Cube
Since, the total surface area of a cube is the area of all its 6 faces, it includes the lateral surface area (LSA). LSA is the area of all faces, excluding the top and the base.
So, LSA = area of the four lateral or side faces
The formula is:
Lateral Surface Area (LSA) = 4a2
Solved Examples
Find the surface area of a cube with side 5 cm.
Solution:
As we know, ∴ Surface Area (SA) = 6a2, here a = 5 cm = 6 × 52 = 150 cm2
Calculate the lateral surface area of a cube with a side length of 9 mm.
Solution:
As we know, Lateral Surface Area (LSA) = 4a2, here a = 9 mm = 4 × 92 = 324 mm2
Find the surface area of cubes with edges 4 cm and 8 in respectively.
Solution:
Here, the measure of two cubes is given. As we know, For one cube, Surface Area (SA) =6a2, here a = 4 cm = 6 × 42 = 96 cm2 For the other cube, Surface Area (SA) = 6a2, here a = 8 in = 6 × 82 = 384 in2
How much marble paper will we need to cover a 6 cm cube-shaped gift box?
Solution:
As we know, The amount of marble paper needed is the surface area of a cube ∴ Surface Area (SA) = 6a2, here a = 6 cm = 6 × 62 = 216 cm2 So we will need 216 cm2 of marble paper to cover the whole cubical gift box.
Finding the Length of EDGE of the Cube when the SURFACE AREA is known
Find the side length of a cube whose area is 625 unit squares.
Solution:
As we know, SA = 6a2 ∴ ${a=\sqrt{\dfrac{SA}{6}}}$, here SA = 625 unit sq. ${\therefore a=\sqrt{\dfrac{625}{6}}}$ ≈ 10.21 units
Finding the SURFACE AREA of the cube when VOLUME is known
Calculate the surface area of a cube given its volume of 343 cm3.
Solution:
Here, we will use an alternative formula. ${ SA=6V^{2/3}}$, here V = 343 cm3 ${\therefore SA=6\times \left( 343\right) ^{2/3}}$ = 294 cm2
