Sides $\mathrm{AB}$ and $\mathrm{BC}$ and median $\mathrm{AD}$ of $\mathrm{a}$
triangle $\mathrm{ABC}$ are respectively proportional to sides $\mathrm{PQ}$ and $\mathrm{QR}$ and median PM of $\Delta$ PQR (see Fig. $6.41$ ). Show that $\Delta \mathrm{ABC}-\Delta \mathrm{PQR}$