At a garden party there are $$7$$ trays of sausages with a mean average of $$13$$ sausages pertray. Just before the guests are allowed in, the head chef brings out another tray containing $$21$$ sausages. What is the mean average number of sausages on the trays now?  Answer:~\uline{~~~~~~~~~~}~ 
Overseas Competition->Knowledge Point->Word Problem Modules->Average Problems ->Using Formulas->Finding the Average Directly