Q160 / 270 · NDA 2010 (Phase 2) · Mathematics
The frequency distribution of life of 90 TV tubes whose median life is 17 months is as follows:
If the area of a triangle with vertices $(-3,0)$, $(3,0)$ and $(0, k)$ is 9 square units, then what is the value of $k$ ?
If the area of a triangle with vertices $(-3,0)$, $(3,0)$ and $(0, k)$ is 9 square units, then what is the value of $k$ ?
- Correct answerA3
- B6
- C9
- D12
Solution
$\begin{aligned} & 9=\frac{1}{2}\left|\begin{array}{ccc}-3 & 0 & 1 \\ 3 & 0 & 1 \\ 0 & k & 1\end{array}\right| \\ & 9=\frac{1}{2}\{-3(-k)-3(-k)+0(0)\} \\ & 9=\frac{1}{2} \times 6 k \\ & \therefore k=3\end{aligned}$
Hence, the correct answer is option: 'A'.