Question : If the surface area of two spheres is in the ratio 81 : 25, then what is the ratio of their radius?
Option 1: 5 : 8
Option 2: 7 : 9
Option 3: 5 : 7
Option 4: 9 : 5
Answer (1)
17th Jan, 2024
Correct Answer: 9 : 5
Solution :
Let the radii of two spheres be $r, R$, respectively.
According to the question,
$\frac{4\pi r^2}{3\pi R^2}=\frac{81}{25}$
$⇒\frac{r^2}{R^2}=\frac{81}{25}$
$\therefore \frac{r}{R}=\frac{9}{5}$
Hence, the correct answer is 9 : 5.
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