Q. The length, width and height of a room is 3,2,1 respectively. The length of the room is doubled and height and width is halved .then percentage decrease in area of wall is

Option
a) 13.6%
b) 27.2%
c) 10%
d) None of these

• If 3x,2x and x are intial dimensions
  and
  6x, x and x/2 are new dimensions, then,
  
  initial area of 4 walls= 2*5x*x = 10x^2
  new are = 2* 7x*x/2 = 7x
  % decrease in area =100*3x/10x= 30% .. none of these
• 12 years agoHelpfull: Yes(27) No(5)
• area = 2(lb+bh+lh)
  l=3,b=2,h=1 area = 2(6+2+3) =22
  when l is doubled i.e l=6,b and h are halved i.e b=1,h=0.5
  area = 2(6+0.5+3) = 19
  decrease in area is ((22-19)/22)=0.1365
  % decrease is 13.65%
  ANS IS a)
• 10 years agoHelpfull: Yes(13) No(9)
• area of room 2(l*b)*h then firstlY the area was 2(3*2)*1=12
  now acording to ur ques h=6 and b=1 and h=1/2 then area 2(6*1)1/2=6
  then area decrese 50%..........
• 11 years agoHelpfull: Yes(4) No(15)
• D.none of these
• 7 years agoHelpfull: Yes(0) No(0)
• in question, it is asked about the area of only walls
  so we know that area of walls=2*(l+b)*h
  hence new area=7
  and old area=10
  decrease in area=10-7=3
  means 30%
  so answer is none of these ......
• 7 years agoHelpfull: Yes(0) No(0)
• LET x BE THE VALUE FOR INITIAL DIMENSION THEN
  3x is LENGTH
  2x is WIDTH
  1x is H EIGHT
  
  AREA OF 4 WALL ROOM IS = 2 * (LENGTH + WIDTH) * HEIGHT
  
  THEREFORE ORIGINAL AREA WILL BE 10x^2
  
  NOW THERE IS A CHANGE IS DIMENSION i.e.
  LENGTH is 6x
  WIDTH is 1x
  HEIGHT is (1/2)x
  
  NEW AREA WOULD BE 7a^2
  
  PERCENTAGE DECREASE IN AREA IS
  
  ( (ORIGINAL AREA - NEW AREA) / (ORIGINAL AREA) ) * 100
  
  ( (10a^2 - 7a^2) / (10a^2) ) *100
  
  ( (3a^2) / (10a^2) ) * 100
  
  30 %
  is the answer
  
  IT MEANS (d) is the ANSWER
• 7 years agoHelpfull: Yes(0) No(0)