Q.If the volumes of two vertical circular cylinders are equal, and their heights are in the ratio 4:9, then the ratio of their radii will be – (a) 3:2 (b) 2:3 (c) 4:9 (d) 8:9
Answer: A
Let the heights be \(4h\) units and \(9h\) units, respectively, and the radii be \(r_1\) and \(r_2\).
According to the condition, \(πr_1^2 \times 4h = πr_2^2 \times 9h\).
Or, \(\cfrac{r_1^2}{r_2^2} = \cfrac{9h}{4h}\).
Or, \(\cfrac{r_1}{r_2} = \sqrt{\cfrac{9}{4}} = \cfrac{3}{2}\).
∴ \(r_1 : r_2 = 3 : 2\).
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