A right circular cylindrical tunnel of diameter 2m and length 40m is to be constructed from a sheet of iron. The area of the iron sheet required in `m^2,` is (a) `40pi` (b) `80pi` (c) `160pi` (d) `200pi`

Explanation

radius of right circular cylindrical tunnel`=1m`

`h=40m`

so curved surface area `=2pirh`

`=2pixx1xx40`

`=80pi`

so area sheet of iron`=80pi`

so ans is b)