Multiple choice

A flower pot in the shape of a frustum with the top and bottom circles of radii $15$ cm and $10$ cm. Its depth is $36$ cm. Find the surface area.

  1. $1,233.5$ $\pi cm^2$
  2. $1,23.5$ $ cm^2$
  3. $1,24.5$ $m^2$
  4. $1,33.5$ $\pi cm^2$
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A Correct answer
Explanation

Surface area of a frustum = pi * (R + r) * l + pi * R^2 + pi * r^2. Slant height l = sqrt(h^2 + (R-r)^2) = sqrt(36^2 + 5^2) = sqrt(1296 + 25) = sqrt(1321) = 36.34. Area = pi * (15+10) * 36.34 + pi * 15^2 + pi * 10^2 = 908.5 * pi + 225 * pi + 100 * pi = 1233.5 * pi.

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