Question

The volume of a room having length, breadth and height in the ratio of 3 : 2 : 1 is 384 contains two windows 3 m * 2 m and two doors 4 m * 2 m. What is the total cost to plaster the 4 walls at Rs 45 per square metre?​

Answer 1

Step-by-step explanation:

Remove area of windows and doors from the area of all walls, hence

Area of paint = area ( 4 walls ) - ( 2 doors + 2 window) ← ( eqⁿ 1)

since , l,b and h are 3:2:1 ratio,

let L = 3x , b = 2x and h = x

therefore, volume = l×b×h

→ 384m² = 3x + 2x + x

→ 6x³ = 384

→ x³ = 384/6 = 64

→ x³ = 4³

x = 4m

now surface area of 4 walls = 2(4 × 8 ) + 2( 12 × 4 )

= 64 + 96

= 160m²

area for paint = 160 - (4 × 2 ) + 2 ( 3 × 2 )

= 160 - ( 16 × 12 )

= 160 - 28

= 132m²

cost of painting 1 sq. m ² = 45

therefore , for 4 walls = rs (45 × 132)

= Rs. 5940

hope this answer helps you dear.....take care and enjoy!