Question

The distance between the directrices of the ellipse $\frac{x^2}{36}+\frac{y^2}{20}=1$ is

• A. 18
• B. 9
• C. 27
• D. 5

Answer 1

Answer: (A)

$e=\sqrt{1-\frac{20}{36}}=\frac{2}{3}$
$\Rightarrow \frac{2a}{e}=\frac{2\times 6}{2}\times 3=18$