Question

EXERCISE 17.4
The length bith and height of a rectangular box are 30 m, 25 mand 18 mespectively
Find the cost of painting its outer surface at 12 per m square.​

Answer 1

Given

• Length, Breadth and Height are 30m, 25m, and 18m Respectively.
• cost of painting = ₹12/m²

Explanation

Firstly, We have to find the total Surface area that defines how much area gonna be painted :-

$\maltese {\large{\pmb{\boxed{\underline{\sf{ T.S.A. _{(Cuboid)} = 2(lb+bh+hl) }}}}}}$

Where as:

• l = Length
• b = Breadth
• h = Height

$\colon\implies{\sf{ T.S.A. _{(Cuboid)} = 2(30 \times 25+25 \times 18+18 \times 30) }} \\ \\ \\ \colon\implies{\sf{ T.S.A. _{(Cuboid)} = 2(750+450+540) }} \\ \\ \\ \colon\implies{\sf{ T.S.A. _{(Cuboid)} = 2(1740) }} \\ \\ \\ \colon\implies{\sf{ T.S.A. _{(Cuboid)} = 3480 \ m^2 }}$

Therefore, Total Surface Area that has to be painted is 3480 m².

Now, We have to find cost needed to paint surfaces as:-

• ₹ 12 per m²

$\colon\implies{\sf{ 12 \times 3480 }} \\ \\ \\ \colon\implies{\sf{ Rs. \ 41760 }}$

Hence,

• Total cost needed to paint box will be ₹ 41760 .

Answer 2

Answer:

Cost of painting its outer surface at 12 per m square is ₹41760

Step-by-step explanation:

Length of a rectangular box (l) = 30 m

Width of a rectangular box (b) = 25 m

Height of a rectangular box (h) = 18 m

Total surface area of the rectangular box = 2(lb+lh+bh)

= 2[(30*25)+(30*18)+(25+18)]

= 2(750+540+450]

= 2(1740)

= 3480

cost of painting its outer surface (12 per m sq)= 12*3480

= 41760