Question

A mettalic pipe is0.7 cm thick. Inner radius of the pipe is 3.5 CM and length is5dm. Find the total surface area

Answer 1

that would be the area of the inner cylinder, plus the area of the outer cylinder, plus the area of the two rings at the end. So, if 
R = outer radius 
r = inner radius 
h = length of pipe 

the total area is 

2πrh + 2πRh + π(R^2-r^2) 
= 2πh(r+R) + π(R+r)(R-r) 
= π(R+r)(2h+R-r)

after putting values you will get the answer

Answer 2

Given,

Thickness of the pipe = 0.7cm

inner radius of the pipe (r )= 3.5cm

External radius of the pipe (R ) = (3.5+ 0.7 )cmor,4.2cm

length=5dm or,50cm

We know,

Total surface area of pipe = 2π (r+ R ) ( h+ R - r)

or, Total surface area of pipe= 2×22/7(3.5+4.2)(50+4.2-3.5)

= 44/7 × 7.7 × 50.7

=2453.88cm^2

So the answer should be 2453.88cm^2

Hope it helps you