In $\Delta ABC$,$m\angle B = 90^{\circ}$ and $\overline{BE}$ is a median. If $AB = 15$ and $BE = 8.5$,find $BC$.

In Figure,$CM$ and $RN$ are respectively the medians of $\Delta ABC$ and $\Delta PQR$. If $\Delta ABC \sim \Delta PQR$,prove that:
$(i)$ $\Delta AMC \sim \Delta PNR$
$(ii)$ $\frac{CM}{RN} = \frac{AB}{PQ}$
$(iii)$ $\Delta CMB \sim \Delta RNQ$

$D, E$ and $F$ are respectively the mid-points of sides $AB, BC$ and $CA$ of $\Delta ABC$. Find the ratio of the areas of $\Delta DEF$ and $\Delta ABC$.

In $\square ABCD$,$\overline{AB} \parallel \overline{CD}$ and $\overline{AC} \cap \overline{BD} = \{M\}$. If $\frac{MB}{MD} = \frac{5}{3}$ and $CD = 12$,find $AB$.

In $\Delta ABC$,$m \angle B = 90^{\circ}$ and $\overline{BM}$ is an altitude to the hypotenuse $\overline{AC}$. If $AM = 12$ and $CM = 3$,find $BM$.

In $\Delta ABC$ and $\Delta PQR$,$\angle A \cong \angle P$ and $\angle B \cong \angle R$. If $AB = 8$,$PQ = 7.5$ and $AC = 6$,find $PR$.