In a triangle $PQR$ right angled at $Q$, $QR=12\;cm$ and $PR=20\;cm$ . Triangle $ABC$ is similar to triangle $PQR$ where the vertices P,Q and R are corresponding to the vertices A,B and C. Each side of $\Delta ABC$ is $\large\frac{1}{4}$ the length of the corresponding slides of $\Delta PQR$. What is the value of $\sin C$ ?