The external diameter of an iron pipe is 20 cm audits length is 12 cm. If the thickness of the pipe is 1 cm. find the surface area of the pipe (take π = $\frac{22}{7}$) correct to two places of decimal.
Answer & explanation
Correct answer: option 2
We know that,
Curved surface of a cylinder = 2πrh
Area of a circle = πR2
We have,
The external diameter of an iron pipe = 20 cm
Length = 12 cm.
Thickness = 1 cm.
External radius of the iron pipe, R = \(\frac{20}{2}\) = 10 cm
Internal radius of the iron pipe, r = 10 - 1 = 9 cm
Height, h = 12 cm
According to the concept = Total surface area of the pipe = Outside surface area + inside surface area + Top Base Area + bottom base area
2πRh + 2πrh + π(R2−r2) + π(R2−r2)
= 2πh(R + r) + 2π(R2−r2)
= 2π {12 × (10 + 9) + (102 - 92)} = 1,552.57 cm2