An edge of a cube is increased by 10%. Find the percent by which the surface area o fa cube has increased?

Answer 1

let each side be x units
surface area = 6x^2

new edge = 1.1x
new surface area = 6(1.1x)^2 = 7.26x^2

increase = 1.26x^2

percentage increase = 1.26x^2/(6x^2) = 1.26/6 = .21
= 21%

we could have just looked at one of the 6 faces for the same result.