An iron pipe 20 cm long has exterior diameter equal to 25cm. If the thickness of the pipe is 1cm, find the whole surface of the pipe.

Explanation

Height of pipe =`20cm`
External diameter=`25 cm`
External radius,`R=25/2`
`R=12.5`
Internal radius = `23/2 = 11.5 cm`
Let the external radius be R and the internal radius be r.
Total surface area of the pipe =` 2pih(R + r) + 2pi(R^2 - r^2)`
`= 2xx22/7xx20(12.5 + 11.5) + 2xx22/7xx{(12.5)^2 - (11.5^2)`
` =(44xx480)/7 + (44xx24)/7`
`=( 21120)/7 + 1056/7`
`=(22176)/7`
` =3168 cm^2`