Multiple choice

A bucket is in the form of a frustum of a cone. The curved surface area of the bucket is 120 $ \pi {cm}^2$. The top and bottom radius of the bucket is 8 and 4 cm. What is the slant height ?

  1. 11 cm

  2. 10 cm

  3. 9 cm

  4. 13 cm
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Curved surface area of a frustum = pi * (R + r) * l. 120 * pi = pi * (8 + 4) * l. 120 = 12 * l. l = 10 cm.

AI explanation

The curved surface area of a frustum of a cone equals pi times the sum of the top and bottom radii times the slant height. We set up the equation 120 times pi equals pi times (8 plus 4) times the slant height. Dividing both sides by pi leaves 120 equal to 12 times the slant height. Dividing 120 by 12 gives a slant height of 10 cm.

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