The length, width, and height of a room are 7 m, 8 m, and 9 m respectively. What is the total area of the walls?

270 Sq m

A shape of room is cuboidal, thus the formulae of total surface area of walls is:

The area of the 4 walls is: l × h + l × h + b × h + b × h

The area of the 4 walls is: 2lh + 2bh

The area of the 4 walls is: 2h (l + b)

So, according to the question:

2h (l + b) = 2 × 9 (7 + 8)

Total area of the walls = 18 (15) = 270 cm²