The school day begins at 7:55 a. m. and ends at 2:40 p. m. how long are you in school?

Think:

7:55 a. m. is 5 minutes (5/60 hrs) before 8 a. m.;

from 8 to noon it's 4 hours, and from noon to 2:40 p. m. is 2 2/3 hours.

Thus, you're in school 5/60 hrs + 4 hrs + 2 2/3 hrs, or

6 2/3 hrs + 5/60 hrs, or 6 40/60 hrs + 5/60 hrs, or

6 45/60 hrs, or 6 3/4 hrs.

Of course there are other ways in which you could do this problem:

4 hrs 5 min plus 2 hrs 40 min comes out to 6 hrs 45 min, or 6 3/4 hrs.