Question

A cube of side equal to 20 cm is open from the top. Its total surface area is __________ cm^2.

(a) 2000

(b) 2400

(c) 2500

(d) 8000

The question was posed to me by my school principal while I was bunking the class.

Query is from Surface Areas and Volumes topic in section Surface Areas and Volumes of Mathematics – Class 9

Answer 1

Correct option is (a) 2000

Easy explanation: The cube is open from the top, hence total surface area of the cube will be equal to 6l^2 – l^2 = 5l^2

= 5(20)^2

= 5(400)

= 2000.