The edge of a cube is increased by 20%. What is the percentage increase in its surface area?

Guest Jun 14, 2020

#1**-1 **

SA of a cube =6a^3, a=edge.

If a = 1, the SA =6

If a =1.2, the SA =6*1.2^3 =10.368

10.368 / 6 =1.728 - 1 x 100 =72.8% increase in SA of the cube.

Guest Jun 14, 2020

#2**0 **

A cube has 6 faces of equal sizes. Each side has area a^{2}, where a is the length of an edge.

Therefore the total surface area of the cube is 6a^{2}.

After increasing the edge length by 20%, the edge is now of length 1.2a.

The new total surface area is 6(1.2a)^{2}, which is (1.2)^{2} = 1.44 times greater than the original.

Therefore the total surface area is increased by (1.44 - 1) = **44%**.

MaxWong Jun 14, 2020