The length, breadth and height of a room are in the ratio 11:5:7. If the breadth is doubled, length

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28 Jun 2019 Area

The length, breadth and height of a room are in the ratio 11:5:7. If the breadth is doubled, length is increased by 4 times while the height is halved. Then the total area of the 4 walls of the room will:

OPtion

1) Increase by 65.00%
2) Increase by 57.50%
3) Increase by 52.25%
4) Increase by 68.75%
5) Increase by 58.25%
6) Increase by 55.25%
7) Increase by 62.75%
8) Increase by 68.25%
9) Increase by 75.65%
10)None of these

Solution

l:b:h=11:5:7


Area of 4 walls = 2*(l+b)*h

Inital Area:
Let h=7x, b=5x and l=11x
Area of 4 walls = 2*(11x+5x)*7x = 224x^2

New dimensions when breadth is doubled, length is increased by 4 times and the height is halved
l1=44x
b1=10x
h1=3.5x

New Area
Area2= 2*(44x+10x)* 7x/2x = 378x^2
% Increase in area = (378 - 224)/224 = 68.75%

Option 4)

Correct Option: 4 Best Solution (1)

SAYAN CHATTERJEE   5 years AGO

Earlier area was (11*7+5*7)*2= 224
New area is (44*3.5+10*3.5)*2= 378
Increase is (378-224)/224= 68.75.
Option 4.

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