Let $\mathrm{G}$ be the centroid of a triangle $\mathrm{ABC}$ and $0 \mathrm{be}$ any other point in that…

Let $\mathrm{G}$ be the centroid of a triangle $\mathrm{ABC}$ and $0 \mathrm{be}$ any other point in that plane, then $\overline{\mathrm{OA}}+\overline{\mathrm{OB}}+\overline{\mathrm{OC}}+\overline{\mathrm{OG}}=$
  1. $4 \overline{\mathrm{OG}}$
  2. $\overline{\mathrm{O}}$
  3. $3 \overline{\mathrm{OG}}$
  4. $2 \overline{\mathrm{OG}}$

Solution

Let $\mathrm{O}$ be the origin. Let $\bar{a}, \bar{b}, \bar{c}$ be the position vectors of vertices $A, B, C$ respectively. $\therefore \overline{\mathrm{OA}}+\overline{\mathrm{OB}}+\overline{\mathrm{OC}}=\overline{\mathrm{a}}+\overline{\mathrm{b}}+\overline{\mathrm{c}}$ Given : $G$ is the centroid of triangle $\begin{array}{l} \therefore \overline{\mathrm{OG}}=\frac{\overline{\mathrm{a}}+\overline{\mathrm{b}}+\overline{\mathrm{c}}}{3} \\ \therefore \overline{\mathrm{a}}+\overline{\mathrm{b}}+\overline{\mathrm{c}}=3 \overline{\mathrm{OG}} \\ \therefore \overline{\mathrm{OA}}+\overline{\mathrm{OB}}+\overline{\mathrm{OC}}+\overline{\mathrm{OG}}=3 \overline{\mathrm{OG}}+\overline{\mathrm{OG}}=4 \overline{\mathrm{OG}} \end{array}$

Asked in: MHT CET 2020 (16 Oct Shift 2)

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