Multiple choice

A hollow cylinder of thickness 0.7 cm and height 15 cm is made of iron. If the inner radius of the cylinder is 3.5 cm, then what is the total surface area (in cm2) of the hollow cylinder?

  1. 812.12

  2. 768.42

  3. 759.88

  4. 828.42
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Inner radius r = 3.5, thickness = 0.7, outer radius R = 4.2. Height h = 15. Total surface area = 2 * pi * R * h + 2 * pi * r * h + 2 * pi * (R^2 - r^2). Area = 2 * pi * 15 * (4.2 + 3.5) + 2 * pi * (17.64 - 12.25) = 2 * pi * 15 * 7.7 + 2 * pi * 5.39 = 231 * pi + 10.78 * pi = 241.78 * pi = 759.88.

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