Ellie and Gloria have to interview a total of $$400$$ people. Ellie can interview $$60$$ people every week. If Gloria and Ellie work together, they can finish all the work in $$4$$ weeks. How many weeks will it take to finish interviewing everyone by Gloria herself? 
Overseas Competition->Knowledge Point->Word Problem Modules->Work Word Problems->Collaborative Work Word Problems
Working together: $$400\div4=100$$ people every week  Gloria: $$100-60=40$$ people every week  $$400\div40=10$$ weeks  $\textasciitilde$ 