Every week, Robyn swims while Sam sings.  For every $$2$$ of Sam\textquotesingle s songs, Robyn swims $$9$$ lengths.  If Robyn swims $$54$$ lengths, how many songs does Sam sing? 
Overseas Competition->Knowledge Point->Word Problem Modules->Unitary Method Problems->Applying Multiplication and Division
Sam sings $$2$$ songs in the time that Robyn swims $$9$$ lengths. The time that she takes for $$54$$ lengths is $$54\div9 =6$$ times longer, so Sam will sing $$2\times6 =12$$ songs. 