Q.If the volumes of two cones are in the ratio 1:4 and the ratio of the diameters of their bases is 4:5, find the ratio of their heights (a) 1:5 (b) 5:4 (c) 5:16 (d) 25:64
Answer: D
Let the heights be \(h_1\) and \(h_2\), and the radii of the bases be \(4r\) and \(5r\), respectively.

∴ \(\cfrac{1}{3} π(4r)^2 h_1 : \cfrac{1}{3} π(5r)^2 h_2 = 1:4\)
or, \(16r^2 h_1 : 25r^2 h_2 = 1:4\)
or, \(\cfrac{16h_1}{25h_2} = \cfrac{1}{4}\)
or, \(\cfrac{h_1}{h_2} = \cfrac{25}{64}\)
Thus, \(h_1 : h_2 = 25:64\).
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