Multiple choice

The radius of a solid right circular cylinder increases by $20\%$ and its height decreases by $20\%$. Find the percentage change in its volume.

  1. $ 15.2$%
  2. $ 17.2$%
  3. $ 19.2$%
  4. $ 21.2$%
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A Correct answer
Explanation

Volume V = pi * r^2 * h. New radius r' = 1.2r, new height h' = 0.8h. New volume V' = pi * (1.2r)^2 * (0.8h) = pi * 1.44 * r^2 * 0.8 * h = 1.152 * V. Change = 15.2%.

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