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