Multiple choice

A right circular cone is 3.6 cm high and radius of its base is 1.6 cm. It is melted and recast into a right circular cone with same radius 1.2 cm. Then the height of the new cone is? / 3.6 सेमी. ऊँचाई तथा 1.6 सेमी. त्रिज्या वाले एक लम्बवृत्तीय शंकु को पिघलाकर एक नया लम्बवृत्तीय शंकु बनाया जाता है, यदि नए शंकु की त्रिज्या 1.2 सेमी. है, तो उसकी ऊँचाई क्या होगी?

  1. 3.6

  2. 4.8

  3. 6.4

  4. 7.2
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Volume of cone = (1/3)πr²h. Original volume: (1/3) × π × (1.6)² × 3.6. New cone has radius 1.2 cm, same volume: (1/3) × π × (1.2)² × h. Equating: (1.6)² × 3.6 = (1.2)² × h. Solving: 2.56 × 3.6 = 1.44h, so h = 9.216/1.44 = 6.4 cm. Option C is correct.

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