The average height of all the teachers in Grape School is $168$. There are $5$ male teachers in Grape School with an average height of $180$. The average height of female teachers is $162$. How many female teachers are there? 
Overseas Competition->Knowledge Point->Word Problem Modules->Average Problems 
Total height less than the average: $(180-168)\times5=60$.  Thus, there are $60\div(168-162)=10$ female teachers. 