Q42 / 160 · WBJEE 2011 · Mathematics
The length of the latus rectum of the ellipse \(16 x^2+25 y^2=400\) is
- A\(5 / 16\) unit
- Correct answerB\(32 / 5\) unit
- C\(16 / 5\) unit
- D\(5 / 32\) unit
Solution
Hints : Length of latus rectum \(=2 \frac{b^2}{a}=\frac{2 \times 16}{5}=\frac{32}{5}\)
\(\begin{aligned}
& 16 x^2+25 y^2=400 \\
& \frac{x^2}{25}+\frac{y^2}{16}=1 \\
& a^2=25 ; b^2=16
\end{aligned}\)
Hence, the correct answer is option: 'B'.