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Question 34 (Choice B) An empty cone of radius 3cm and height 12cm is filled with ice-cream such that the lower part of the cone which is (1/6)th of the volume of the cone is unfilled (empty) but a hemisphere is formed on the top. Find the volume of the ice-cream.Now, Volume of ice-cream = Volume of hemisphere of radius 3 cm + Volume of cone – 1/6 × Volume of cone = Volume of hemisphere of radius 3 cm + 𝟓/𝟔 × Volume of cone Volume of hemisphere Radius of hemisphere = r = 3 cm Volume of the hemisphere = 2/3 πr3 = 2/3 × 𝜋 × 3^3 = 2/3× 𝜋 × 3 × 3 × 3 = 2 × 𝜋 × 3 × 3 = 18𝝅 cm3 Volume of cone Height of cone = h = 12 cm Radius of cone = r = 3 cm Now, Volume of cone = 1/3 𝜋𝑟2ℎ = 1/(3 )× 𝜋 × (3)2 × 12 = 𝜋 × 3 × 12 = 36𝝅 cm3 Now, Volume of ice-cream = Volume of hemisphere of radius 3 cm + 5/6 × Volume of cone = 18𝝅 + 𝟓/𝟔 × 36𝝅 = 18𝜋 + 5 × 6𝜋 = 18𝜋 + 30𝜋 = 48𝝅 cm3 Putting 𝜋=3.14 = 48 × 3.14 cm3 = 150.72 cm3 (approx)

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 15 years. He provides courses for Maths, Science and Computer Science at Teachoo