Question

The external diameter of an iron pipe is 25 cm and its length is 20 cm. If the thickness of the pipe is 1cm, find the total surface area of the pipe ​

Answer 1

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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

Step-by-step explanation:

Height = 20 cm

External diameter = 25 cm

External radius = 25/2 = 12.5 cm

Inter 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