In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.

[Q]: Plasma levels fall by about a half within three to _ hours.
[A]: four


[Q]: Black adults have three to _ times greater incidence of bacteremia, compared with white adults.
[A]: five


[Q]: Some dentists prefer using the oral rinse for _ to five days at a time.
[A]:
three