Two ice cream machines make a total of 320 gallons in a certain amount of time. Working together for the same length of time, how many gallons of ice cream can 12 ice cream machines make?
If two ice cream machines make a total of 320 gallons, then each ice cream machine makes 320/2 = <<320/2=160>>160 gallons.
Working together for the same length of time, 12 ice cream machines can make a total of 160*12 = <<160*12=1920>>1920 gallons of ice cream. Answer: \boxed{1920}.