The sum of the dimensions of a room (i.e. length, breadth and height) is 18 metres and its length, breadth and height are in the ratio of 3…

Solution
Let the dimension of the room be $3x , 2x , x$ metres
Acc. to ques, => $3x + 2x + x = 18$
=> $x = \frac{18}{6} = 3$ metres
Curved surface area of the room = $2 h (l + b)$

= $2 \times x \times (3x + 2x) = 2x \times 5x$
= $10 (x)^2 = 10 \times (3)^2$
= $10 \times 9 = 90 m^2$
$\therefore$ Total cost incurred on painting only the four walls of the room = $15 \times 90$
= $Rs. 1,350$