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Question

The radius of a cylinder is increased by 33 % and its height is decreased by x% such that the volume of the cylinder remains unchanged. Find x.

This question was previously asked in
RRB Group D 2025 Question Paper (18-Aug-2026) (Shift 1)
The correct answer is

43.75

Volume of a cylinder V = πr²h. After change, new radius = 1.33 r, so new r² = (1.33)² r² = 1.7689 r².

For V to stay the same, new h × 1.7689 = old h, so new h = old h / 1.7689 ≈ 0.5625 × old h.

Reduction in h = 1 − 0.5625 = 0.4375, i.e. 43.75%.

Hence, the answer is 43.75.

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