A dataset of $9$ numbers has an average of $72$. After removing one of the numbers, the average of the remaining numbers becomes $78$. The number that gets removed is~\uline{~~~~~~~~~~}~. 
Overseas Competition->Knowledge Point->Counting Modules->Statistics and Probability->Basic Concepts of Statistics
$$9\times72=648$$  $$78\times8=624$$  $$648-624=24$$ 