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

Answer:

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.

Answer 2

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Total Surface Area

= 2πh(R+r) + 2π(R²-r²)

• Putting the given value in above formula , we get

= 3168 cm²