Multiple choice

Radius of a cylindrical jar is increased by 25%. By what percent must the height be decreased so that there is no change in its volume?

  1. 25%

  2. 26%

  3. 40%

  4. 36%

  5. 52%
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Volume of cylinder = πr²h. If radius increases by 25%, new radius = 1.25r, so new radius factor = 1.25² = 1.5625. To keep volume constant: πr²h = π(1.25r)²(h_new) = π × 1.5625r² × h_new. Therefore h_new = h/1.5625 = 0.64h. The height decreases by 1 - 0.64 = 0.36 = 36%. The answer 36% is correct.

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