Question

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

Answer 1

Answer:

Solution:-

Height of pipe = 20 cm

External diameter = 25 cm 

External radius = 25/2 = 12.5 cm

Internal diameter = 25 - (1 + 1)

= 23 cm

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 = 2πh(R + r) + 2π(R² - r²)

⇒ 2*22/7*20(12.5 + 11.5) + 2*22/7*{(12.5)² - (11.5²)

⇒ (44*480)/7 + (44*24)/7

⇒ 21120/7 + 1056/7

⇒ 22176/7

= 3168 cm²

So, the total surface area of the pipe is 3168 square cm.

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Answer 2

Answer:

the pipe is 20cm long extension diameter is 25cm ,thickness is 1 cm,

exterior radius 25/2 cm

interior radius =25/2 –123/2cm

the total surface area is

=exterior surface area of the pipe + interior surface of the pipe + two end of the pipe (thickness area)

=2 pie (r) .1 + 2 pie (r) .1 +2(pie (r²) – pie (r²) )

=2 pie ( 1(R+r) + ( R+r) ( R–r)

=2 pie (R+r)(l+r–r)

2×22/7×(25/2+23/2) (20+25/2–23/2)

= 44×72

=3168so,the total surface area is3168 sq. units