Multiple choice

If the radius of the base of a right circular cylinder is increased by 20% and the height is decreased by 30%, then what is the percentage increase/decrease in the volume?

  1. Decrease 0.8%

  2. Increase 2%

  3. Increase 0.8%

  4. Decrease 2%
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Original volume V = πr²h. New radius = 1.2r, new height = 0.7h. New volume = π(1.2r)²(0.7h) = π × 1.44r² × 0.7h = 1.008πr²h = 1.008V. This represents a 0.8% increase (1.008 - 1 = 0.008 = 0.8%).

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