Answer:
Explanation:
Given,
Outer diameter = 18 cm
∴Outer Radius, R = 9 cm
Thickness = 2 cm
∴Inner Radius, r = 9 - 2 = 7cm
Height = 4cm
Now,
Since the pipe has some thickness, so we can't use the direct formula for total surface area.
Instead, we will find the curved surface area of in and out, the area of the top and bottom parts, and we will add them.
Curved Surface area,
= 2πrh + 2πRh [CSA = 2πrh]
= 2πh(r+R)
Now, area of top and bottom pipe surfaces,
= (Area Outer circle - Area inner circle)
= 2πR² - 2πr² [Area of circle = 2πr²]
= 2π(R² - r²)
= 2π(R + r)(R - r) [a² - b² = (a+b)(a-b)]
Therefore, total area,
= 2πh(r+R) + 2π(r + R)(R - r)
=2π(r + R)[h + (R - r)]
=2π(16)(6)
=2(22/7)(16)(6)
=603.42
And if we use pi = 3.14,
2π(16)(6)
=2(3.14)(16)(6)
=602.88