The length breadth and height of a room are in the ratio 3 : 2 : 1. If the breadth and height are halved while the length is doubled, then total area of the four walls of the room will (1) Remain the same (2) Decrease by 30% (3) Decrease by 15% (4) Decrease by 18.75%

Answer: (2)

Let us consider the room with

Length (l) = 3x

Breadth (b) = 2x

Height = 1x

Area of the walls (A) = 2(l + b) × h

A = 2(3x + 2x) × 1x

A = 10x2 sq. unit.


l1 = 6x

b1 = x

h1 = x/2

Nwe area (A1) = 2(6x + x) (x/2)

A1 = 7x2

\(\begin{array}{l}% decrease in the area of walls = \frac{10x^{2}-7x^{2}}{10x^{2}}\end{array} \)

% decrease in the area of walls = 30%

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  1. Suppose we have a square ABCD measuring sides be (x+1). If we draw a diagonal BC calculate the diagonal by using Pythagoras theorem.

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