Question

Total surface area of a cube having sides l is given by __________

(a) l*b*h

(b) 2(lb + bh + lh)

(c) lb + bh + lh

(d) 6l^2

The question was posed to me during an internship interview.

The above asked question is from Surface Areas and Volumes topic in portion Surface Areas and Volumes of Mathematics – Class 9

Answer 1

Right choice is (d) 6l^2

To elaborate: A cube has six equal sides.

Hence, total surface area of a cube = sum of areas of 6 sides (as shown in the figure below)

Area of one side of a cube having side equal to ‘l’ = l^2

Total surface area of the cube = l^2 + l^2 + l^2+l^2+ l^2 + l^2

= 6l^2.