We have a 345 gallon hot tub that fills at a rate of 3.61 gallons/min.
To calculate filling time, we need to divide as it follows:

in that way we can find how much time does it take in minutes

now, if we want to determine time in hours, we must divide by 60, because there are 60 min. in one hour.

Then, it would take approximately 1.59 hours to fill the hot tub.