[Ratio of areas of triangles with a common angle]

Heron's formula

Points $Q$ and $R$ are located on sides $M N$ and $M P$ of triangle $M N P$, respectively, such that $M Q=3, M R=4$. Find the area of triangle $M Q R$, if $M N=4, M P=5, N P=6$.
$s_{\Delta \mathrm{MQR}}=\frac{M Q}{M N} \cdot \frac{M R}{M P} \cdot s_{\Delta \mathrm{MNP}} \cdot$

## Answer

$\frac{9 \sqrt{7}}{4}$.