Q113 / 160 · AP EAMCET 2020 (17 Sep Shift 2) · Mathematics
If \(\overline{\mathbf{P O}}+\overline{\mathbf{O Q}}=\overline{\mathbf{Q O}}+\overline{\mathbf{O R}}\), then
- Correct answerA\(Q\) is the mid-point of \(\overline{P R}\)
- B\(Q\) divides \(\overline{\mathrm{PR}}\) in \(2: 1\)
- C\(Q\) divides \(\overline{\mathrm{PR}}\) in \(1: 2\)
- D\(Q\) divides \(\overline{\mathrm{PR}}\) in \(-1: 2\)
Solution
From diagram below,

Using triangle law, \(\begin{aligned} & \quad \mathbf{P O}+\mathbf{O Q}=\mathbf{Q P} \text { and } \mathbf{Q O}+\mathbf{O R}=\mathbf{Q R} \\ & \text {Given; } \mathbf{P O}+\mathbf{O Q}=\mathbf{Q O}+\mathbf{O R} \Rightarrow \mathbf{Q P}=\mathbf{Q R} \\ & \Rightarrow \quad|\mathbf{Q P}|=|\mathbf{Q R}| \Rightarrow Q P \text { length }=Q R \text { length } \\ & \therefore Q \text { is mid point of } \mathbf{P R} \end{aligned}\)

Using triangle law, \(\begin{aligned} & \quad \mathbf{P O}+\mathbf{O Q}=\mathbf{Q P} \text { and } \mathbf{Q O}+\mathbf{O R}=\mathbf{Q R} \\ & \text {Given; } \mathbf{P O}+\mathbf{O Q}=\mathbf{Q O}+\mathbf{O R} \Rightarrow \mathbf{Q P}=\mathbf{Q R} \\ & \Rightarrow \quad|\mathbf{Q P}|=|\mathbf{Q R}| \Rightarrow Q P \text { length }=Q R \text { length } \\ & \therefore Q \text { is mid point of } \mathbf{P R} \end{aligned}\)
Hence, the correct answer is option: 'A'.