Multiple choice general knowledge math & puzzles

If the diameter of a wire is increased by 10%, by how much per cent approximately, will its length be decreased, if the volume remains the same?

  1. 15

  2. 16

  3. 17

  4. 18
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Volume V = π(d/2)^2 * h. If d increases by 10% (1.1d), the new area is 1.21 times the old area. To keep volume constant, the new length must be 1/1.21 of the old length (~0.826), a decrease of ~17.36%.

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