Multiple choice

Radius and height of a cylinder is increased by 30%. Find the percentage change in its total surface area. एक बेलन की त्रिज्या और ऊंचाई में 30% की वृद्धि हुई है। इसके कुल पृष्ठ क्षेत्रफल में प्रतिशत परिवर्तन ज्ञात कीजिये।

  1. 69%

  2. 54%

  3. 81%

  4. 64%
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A Correct answer
Explanation

When radius and height both increase by 30%, they become 1.3 times their original values. Total surface area = 2πr² + 2πrh. New TSA = 2π(1.3r)² + 2π(1.3r)(1.3h) = 1.69(2πr² + 2πrh) = 1.69 × original. The increase is (1.69 - 1) × 100% = 69%. Both terms of the surface area formula are multiplied by 1.3².

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