If the radius of the base of a right circular cylinder is decreased by 27% and its height is increased by 237%, then what is the percentage increase (closest integer) in its volume?

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  1. 80%
  2. 97%
  3. 95%
  4. 87%

Answer (Detailed Solution Below)

Option 1 : 80%
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Detailed Solution

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Given:

Initial radius of the cylinder = r.

Initial height of the cylinder = h.

Radius decreased by 27%, so new radius = 73% of r = 0.73r.

Height increased by 237%, so new height = 337% of h = 3.37h.

Formula Used:

Volume of a right circular cylinder = πr2h.

Calculation:

Initial Volume = πr2h.

New Volume = π(new radius)2(new height).

New Volume = π(0.73r)2(3.37h).

New Volume = π(0.732 × r2)(3.37h).

New Volume = π(0.5329 × r2)(3.37h).

New Volume = π(1.796873 × r2h).

Percentage Increase = [(New Volume - Initial Volume) / Initial Volume] × 100.

Percentage Increase = [(π(1.796873 × r2h) - πr2h) / (πr2h)] × 100.

Percentage Increase = [(1.796873 - 1) / 1] × 100.

Percentage Increase = 0.796873 × 100.

Percentage Increase ≈ 80%.

The percentage increase (closest integer) in the volume is approximately 80%.

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