1000ml x 15 gtt x 1 hr = 31 gtt

8hr ml 60 min

How do you do this???

beats me. you want to explain in words what you are trying to solve?

Like, how long does it take to administer 1000ml at 15 drops per hour, or something like that?

Your units are all mixed up.

On the left, you have ml*gtt*hr
On the right you have ml*gtt*hr*min

I think you need some divsions inthere somewhere