Question

The length, breadth and height of a room are 5m,4m and 3m respectively.find the cost of white washing the walls and the ceiling at the rate of ₹7.50 per m^.​

Answer 1

Answer:

Step-by-step explanation

Length=5m

Breadth=4m

Height=3m

Lateral Surface Area= 2h (l+b)

=2×3(5+4)m sq.

=6×(9)m sq.

=54m sq.

Area of the ceiling= l×b

=5×4

=20m sq.

Total area needed to be whitewashed= 54 + 20 m sq.

=74m sq.

Cost of whitewashing 1 m sq.= Rs. 7.50

Cost of whitewashing 74m sq.= 74 × 7.50

= Rs. 555.0

Therefore answer : Rs.555

Hope this helped you

Answer 2

✬ Cost = Rs 555 ✬

Step-by-step explanation:

Given:

• Length (l) , breadth (b) and height (h) of room are 5m ,4m and 3m respectively.
• Cost of white washing is Rs 7.50 m².

To Find:

• What is the cost of white washing the walls and ceiling ?

Solution: As we know that the formula for area of four walls of room is

★ Area of four walls of room = 2h ( l + b) sq units ★

$\implies{\rm }$ Area of four walls = 2 $\times$ 3 ( 5 + 4 ) m²

$\implies{\rm }$ ( 6 $\times$ 9 ) m²

$\implies{\rm }$ 54 m²

So, the area of four walls of the room is 54 m².

Formula for area of ceiling of room is -

★ Area of ceiling = ( L x B ) sq units. ★

• Since, the ceiling is in rectangular form.

$\implies{\rm }$ Area of ceiling = ( 5 x 4 ) m²

$\implies{\rm }$ 20 m².

➱ Area of whole room = Area ( Four walls + Ceiling )

➱ Area of whole room = ( 54 + 20 ) m² = 74 m².

• Cost of white washing for 1 m² = Rs 7.50

∴ Cost of white washing for 74 m² = 7.50 x 74 = Rs 555 .

Hence, the cost of white washing the room at 7.50 /m² is Rs 555.

____________________

➼ Or, simple we can find the area of whole room by using this formula

★ 2h ( l + b ) + l x b ★

➟ { 2 $\times$ 3 ( 5 + 4 ) + 5 $\times$ 4 } m²

➟ { 6 $\times$ 9 + 20 } m²

➟ { 54 + 20 } m²

➟ 72 m²