Multiple choice

Calculate the total surface area of a frustum of cone whose upper base radius is 15 m and lower base radius is 5 m and its height is 15 m. (Use $\pi$ = 3).

  1. 1,931.66 m$^2$
  2. 1,831.66 m$^2$
  3. 1,731.66 m$^2$
  4. 1,631.66 m$^2$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Total surface area = pi * (R^2 + r^2 + (R+r)*l). l = sqrt(h^2 + (R-r)^2) = sqrt(15^2 + 10^2) = sqrt(325) = 18.027. Using pi = 3: Area = 3 * (15^2 + 5^2 + (15+5)*18.027) = 3 * (225 + 25 + 360.54) = 3 * 610.54 = 1831.62. Matches option B.

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