TITLE: Ceiling and floor functions
QUESTION [7 upvotes]: What are some real life application of ceiling and floor functions?
Googling this shows some trivial applications.

REPLY [4 votes]: Suppose a telephone company charges you 0.25 dollar for every minute. Now, you talk 5 minutes and you are charged 1.40 dollar.
But 5 x 0.25 = 1.25
They use ceiling function to make it 1.40 dollar.
Or, suppose they give you an offer to talk 5 minutes for 1.00 dollar. Then they are using floor function.