Question

The length, breadth and height of a room are 5 m, 4 m and 3 m respectively. Find the cost of white washing the walls of the room and the ceiling at the rate of Rs. 7.50 m².

Answer 1

$\huge \underline \mathbb {SOLUTION:-}$

Given:

• Length (l) of room = 5m

• Breadth (b) of room = 4m

• Height (h) of room = 3m

It can be observed that four walls and the ceiling of the room are to be white washed.

Total area to be white washed = Area of walls + Area of ceiling of room

= 2lh + 2bh + lb

= [2 × 5 × 3 + 2 × 4 × 3 + 5 × 4]

= (30 + 24 + 20)

= 74

Area = 74 m²

Also,

Cost of white wash per m² area = Rs.7.50 (Given)

Cost of white washing 74 m² area = Rs.(74 × 7.50)

= Rs. 555

Answer 2

SOLUTION:

Given :

Length of the room, (L) = 5 m

=Breadth of the room, (B)

= 4 m Height of the room, (H)

= 3 m • Rate of ceiling = 7.50 /m?

=Explanation :

As we know that formula of the total surface area of ceiling of white washing;

$\sf\boxed{S.A. of 4 walls = 2(1+b)h + lb}$

SURFACE AREA OF PAINTED WALL

$\sf\boxed{ = 2(l + b)h + lb}$

$\sf \boxed{ = 2(5 + 4)3 + 5 \times 4}$

$\sf \boxed{ = 2(9)3 + 5 \times 4}$

$\sf \boxed{ = 54 + 20}$

AREA OF PAINTED WALL= 74m²

TOTAL COST = RATE ×AREA

$\sf \boxed{7.50 \times 74}$

TOTAL COST = 555 Rs

TOTAL COST FOR WHITE WASHING WALL = 555