A right circular cylindrical tunnel of diameter 2 m and length 40 m is to be constructed from a sheet of iron. The area of the iron sheet required in m2, is
(a) 40 π (b) 80 π
(c) 160 π (d) 200 π
Diameter of a cylindrical tunnel = 2 m
∴ Radius (r) =22=1 m
and length (h) = 40 m
Curved surface area = 2π r h
= 2×π×1×40=80π
Hence the correct answer is (b) 80 π