Question

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

Answer 1

Step-by-step explanation:

The pipe is 20cm long (l)

extension diameter is 25cm, thickness is 10m.

∴ exterior radius (R)=

2

25

cm

interior radius (r)=

2

25

−1=

2

23

cm

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(πr

2

−πr

2

)

=2π[l(R+r)+(R+r)(R−r)]

=2π(R+r)(l+R−r)

=2×

7

22

×(

2

25

+

2

23

)(20+

2

25

−

2

23

)

=

7

44

×24×21

=44×72

=3168