How many hours is 9 a.m. to 9 p.m.?

Answer 1

From 9:00 A.M. to 6:30 P.M. the same day is 9½ hours.

9:00 A.M. to noon is 3 hours, and noon to 6:30 P.M. is 6½ hours, so 3 + 6½ = 9½ hours.

Answer 2

Whatever that number was going to be, just add three to it.

Answer 3

12 hours