The pipe is
20cm long
(l)extension diameter is 25cm, thickness is 10m.
∴ exterior radius (R)=252cm
interior radius (r)=252−1=232cm
So, the total surface area is
= exterior surface of the pipe +
interior surface of the pipe +
two ends of the pipe (thickness area)
=2π(R).l+2π(r).l+2(πr2−πr2)
=2π[l(R+r)+(R+r)(R−r)]
=2π(R+r)(l+R−r)
=2×227×(252+232)(20+252−232)
=447×24×21
=44×72
=3168
So, the total surface face area is 3168 sq.cm.