What will be the cost of the painting the four walls of a room with length ,width and height is 5,3,8 meters respectively. The room has one window and one door.
I.Cost of painting per square meter is Rs 25
II.Area of window is 2.25 sq m which is half of the area of the door
III.Area of the room is 15 sq meter

Length = 5 m , Breadth = 3 m and Height = 8 m

To find the cost of painting the walls of the room, we should know the cost of painting and the area of door and window.

Area of 4 walls (Curved Surface Area of cuboid) = $$2h(l+b)$$

= $$(2 \times 8)(5+3) = 16 \times 8 = 128$$ $$m^2$$

From I & II : Cost = Rs 25 per square meter

Area of window = $$2.25$$ $$m^2$$

and Area of door = $$2 \times 2.25 = 4.5$$ $$m^2$$

Thus, area to be painted = $$128 - 2.25 - 4.5 = 121.25$$ $$m^2$$

$$\therefore$$ Cost of painting 4 walls = $$25 \times 121.25 = Rs$$ $$3031.25$$

Thus, statement III is redundant.

=> Ans - (C)