16Hit1600
Geometry and TrigonometryVery hardEffect of doubling the radius of a cylinder

Geometry and Trigonometry practice question

A cylindrical tank's radius is doubled while its height stays the same. How does the volume change?

  1. A. It becomes 4 times as large.Correct
  2. B. It doubles.
  3. C. It becomes 8 times as large.
  4. D. It becomes 6 times as large.

Answer: A. It becomes 4 times as large.

V = πr²h. Doubling r multiplies r² by 4, so the volume is 4 times as large.

Why the other answers are wrong

B. It doubles.
Doubling would apply if volume scaled with r, but it scales with r².
C. It becomes 8 times as large.
8 times would need all three dimensions doubled.
D. It becomes 6 times as large.
6 has no basis; (2r)² = 4r².

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