Question:
Two circular cylinders of equal volumes have their heights in the ratio 1 : 2. Find the ratio of their radii.
Solution:
Here, V1 = Volume of cylinder 1
V2 = Volume of cylinder 2
r1 = Radius of cylinder 1
r2 = Radius of cylinder 2
h1 = Height of cylinder 1
h2 = Height of cylinder 2
Volumes of cylinder 1 and 2 are equal.
Height of cylinder 1 is half the height of cylinder 2.
∴ V1 = V2
(πr12h1) = (πr22h2)
(πr12h) = (πr222h)
$\frac{r_{1}{ }^{2}}{r_{2}{ }^{2}}=\frac{2}{1}$
$\frac{r_{1}}{r_{2}}=\sqrt{\frac{2}{1}}$
Thus, the ratio of their radii is $\sqrt{2}: 1$.
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