It takes $$144$$ workers $$60$$ hours to paint a bridge. Working at the same rate, how many hours would $$108$$ workers require to do the job? 
Overseas Competition->Knowledge Point->Word Problem Modules->Unitary Method Problems->Finding the Total Value using Unitary Method
It takes $$144$$ workers $$60$$ hours to paint a bridge. That\textquotesingle s $$144\times60=8640$$ worker-hours. For $$108$$ workers, the job takes $$8640\div108=80$$ hours. 