Find the median weight for the following data:
$$\begin{aligned} &\begin{array}{|l|c|c|c|c|c|c|c|} \hline \text { Weight (in } \mathrm{kg} \text { ) } & 45 & 46 & 48 & 50 & 52 & 54 & 55 \\ \hline \text { Number of boys } & 8 & 5 & 6 & 9 & 7 & 4 & 2 \\ \hline \end{array} \end{aligned}$$