The length of a room exceeds its breadth by 2 metres. If the length i...
Let the breadth (b) of the room be 'x' metres
Then, length (l) of the room = (x + 2) metres
Area (A) = l × b = x(x + 2) m2
Given, length is increased by 4 metres and the breadth is decreased by 2 metres
Then, new length (l') of the room = (x + 6) metres
New breadth (b') of the room = (x - 2) metres
New Area (A') of the room = l' × b' = (x + 6) (x - 2) m2
Also given that, A = A'
Or x (x + 2) = (x + 6) (x - 2)
x2 + 2x = x2 + 4x - 12
2x = 12
x = 6
Therefore, the length of the room (l) = 8 metres
And breadth of the room (b) = 6 metres
And given height of the room (h) = 3 metres
Since the room will be in the shape of a cuboid,
Surface area of walls = 2(l + b)h
= 2(8 + 6)3 m2
= 84 m2
Hence, answer option 4 is correct.