Step 1: Understand the impact of scientific management on working hours.
Scientific management aims to increase productivity, which typically leads to the reduction of working hours. By optimizing tasks, workers can complete their duties more efficiently.
Step 2: Evaluate the options.
- Through better work processes, scientific management helps reduce the time spent on tasks, ultimately decreasing the working hours needed.
Step 3: Conclude.
The correct answer is that scientific management decreases the working hours of workers.
Final Answer:
\[
\boxed{\text{Decreased}}
\]