Multiple choice

Find the surface area of a frustum of cone, whose larger and smaller radius is 12 and 5 m. The slant height of the cone is 20 m.

  1. 519$\pi$ m$^2$
  2. 509$\pi$ m$^2$
  3. 529$\pi$ m$^2$
  4. 539$\pi$ m$^2$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Surface area of frustum = pi * (R+r) * l + pi * R^2 + pi * r^2. R=12, r=5, l=20. Area = pi * (12+5) * 20 + pi * 144 + pi * 25 = 340pi + 144pi + 25pi = 509pi.

AI explanation

The curved surface area of a frustum of a cone is given by the formula pi times the sum of the two radii times the slant height. Substituting the values, we get pi times (12 plus 5) times 20, which equals 340 times pi. The areas of the top and bottom circular bases are pi times 12 squared and pi times 5 squared, equaling 144 times pi and 25 times pi. The total surface area is the sum of the curved area and the base areas, so 340 times pi plus 144 times pi plus 25 times pi equals 509 times pi square meters.

Keep practicing — related questions