If workers become more efficient and complete the task in 4 hours instead of 6 hours, how does it affect the total man-hours?

When workers complete a task in less time, the total man-hours required for that task decreases. Man-hours are calculated by multiplying the number of workers by the time they spend on the task. In this scenario, if originally a group of workers takes 6 hours to complete the task, the total man-hours would be the number of workers multiplied by 6 hours.

When the efficiency increases and the task is performed in just 4 hours, the same group of workers will now complete the task with fewer total hours required. This reduction in the time taken signifies a decrease in the overall man-hours needed for the task, hence the correct choice reflects that total man-hours decrease when workers are able to perform a task more efficiently.

In this case, both the total productivity and the time taken are essential in calculating man-hours, with the time reduction leading directly to a decrease in the man-hours required to complete the same task.