Master Zhang plans to bind a batch of books in three hours. When there are 120 books left, the efficiency of the binding machine in the library is reduced by one fifth, and the result is higher than t
Master Zhang plans to bind a batch of books in three hours. When there are 120 books left, the efficiency of the binding machine in the library is reduced by one fifth, and the result is higher than the original plan.
120 ÷ (1-1/5) =120 ÷ 4/5 = 150. After reducing the efficiency, the time for binding120 copies is equal to the original binding. It should take 4/3 minutes to bind 1, 3× 60 ÷ 4/3 =180 ÷ 4/3 = 135, but the original binding was135.