Question

A room is 9 m long, 8 m broad and 6.5 m high. It has one door of dimensions
2m x 1.5 m and three windows each of dimensions 1.5 m x 1 m. Find the cost of white
washing the walls at Rs 3.80 per square metre.

Please explain me And I will mark you as brainliest​

Answer 1

Are of door = $l*b$

                   = $2*1.5$

                   = $3m^{2}$

Area of 1 window = $l*b$

Area of 3 windows = $3*l*b$

                               = $3*1.5*1$

                               = $4.5m^{2}$

Lateral surface area (LSA) of the cuboidal room = $2h(l+b)$

[LSA ∵ white washing is only of walls]                 = $2*6.5(9+8)$

                                                                                = $13*17$

                                                                                = $221m^{2}$

∴ Area of whitewashing = 221 - (4.5 + 3)

                                        = 221 - 7.5

                                        = $213.5m^{2}$

Cost of whitewashing $1m^{2}$ = ₹ 3.80

∴ Cost of white washing $213.5m^{2}$ =  213.5 * 3.80

                                                      =  ₹ 811.3

Ans:- ∴ Cost of whitewashing the walls is

₹ 811.3