Question

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

Answer 1

Area of wall of room of length, width & height $3, 2. 1$ respectively is

$=2(3\cdot 2+2\cdot 1+3\cdot 1)$

$=22$

Now, after changing dimensions, the area of wall of room of length, width & height $6, 1. 1/2$ respectively is

$=2(6\cdot 1+1\cdot 1/2+6\cdot 1/2)$

$=19$

The percentage decrease in the area of wall

$=\frac{22-19}{22} \times 100$

$=13.63$