The length breadth and height of a room are in the ratio 7 3 1 If the breadth and height are doubled...........

Quantitative Aptitude ( CCS) Mensuration 3D

The length, breadth and height of a room are in the ratio 7:3:1. If the breadth and height are doubled while the length is halved, then by what percent the total area of the 4 walls of the room will be increased ?

50%

60%

70%

90%

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Explanation:

Let length, breadth and height of the room be 7, 3, 1 unit respectively.
Area of walls = 2(l+b)xh = 2(7+3)x1 = 20 sq. unit.
Now, length, breadth and height of room will become 3.5, 6 and 2 respectively.
Area of walls = 2(l+b)xh = 2(3.5+6)x2 = 38 sq. unit.
% Increase in the area of walls = (38-20)x100/20 = 90%.