Multiple choice

Find the difference between total surface area & curved surface area of a hemisphere of radius $21\space cm$.

  1. $1376\space cm^2$
  2. $1386\space cm^2$
  3. $1396\space cm^2$
  4. $1404\space cm^2$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Total surface area of a hemisphere is 3 * pi * r^2. Curved surface area is 2 * pi * r^2. The difference is pi * r^2. With r = 21, difference = (22/7) * 21 * 21 = 22 * 3 * 21 = 1386 cm^2.

AI explanation

The total surface area of a hemisphere of radius r is 3 * pi * r^2, while its curved surface area is 2 * pi * r^2. The difference between the total surface area and the curved surface area is simply the area of its circular base, which is pi * r^2. Substituting the given radius of 21 cm, the difference is (22/7) * 21^2. This simplifies to 22 * 3 * 21, resulting in 1386 square centimeters.

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