Q:
      
      
         
            
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  ?
         
       
      
      
      
          
      
      
          Answer & Explanation
         Answer: A) 90%         
         
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%.
       
      
      
      
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