Question

If one litre of paint covers 10 m^2 , how many litres of paint is requried to paint the internal and external surface areas of a cylinderical tunnel whose thickness is 2m , internal radius is 6 m and height is 25m.​

Answer 1

Answer:

220 Litres

Step-by-step explanation:

First Curved Surface Area (CSA) of internal part of tunnel should be found

2πrh - formula for csa

Internal surface area :

2 X 22/7 X 6 x 6 m^2

Thickness = 2 m

So the external radius =  6m + 2m(thickness) = 8 m

2πrh - formula for csa

External Surface Area :

⇒ 2 x 22/7 x 8 x 8

Adding both of these gives  the area to be painted:

2 x 22/7 x 6 x 6 + 2 x 22/7 x 8 x 8

⇒ 6600/7 +  8800/7

⇒ 15400/7  = 2200 m^2

If 1 litre can cover 10m^2

then 2200m^2/10 gives no of litres of paint required

   ∴220 litres of paint is required to paint the internal and external surface     areas of the  tunnel.