The base radius and height of a cone are doubled. The ratio of the new volume to original volume is?

8 : 7
8 : 3
8 : 1
8 : 5

Correct Answer: 8 : 1

Explanation:

Let original radius = r and height = h
Original volume = (1/3)πr²h
New radius = 2r and new height = 2h
∴ New volume = 1/3 x π(2r)² x 2h = 8/3πr²h
Required ratio = 8/3πr²h : 1/3πr²h = 8 : 1

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