Multiple choice

If volume and surface area of a sphere are numerically equal then it's radius is

  1. $2\ units$
  2. $3\ units$
  3. $5\ units$
  4. $8\ units$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

(4/3)pi r^3 = 4pi r^2. Dividing by 4pi r^2 gives r/3 = 1, so r = 3.

AI explanation

The formula for the volume of a sphere is (4/3)*pi*r^3 and the formula for its surface area is 4*pi*r^2. Setting them equal gives (4/3)*pi*r^3 = 4*pi*r^2. Dividing both sides by 4*pi*r^2 leaves r/3 = 1, meaning r = 3. The result is 3 units.

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