It is known that
450 gallons/min=2acre-feet/24hours
Now we have to convert 24 hours to minutes
[tex]24\text{hours}\times\frac{60\min}{1\text{ hour}}=1440\min [/tex]It means that 2acre-feet/24 hours=2acre-feet/1440min, solving the quotient we have that
2 acrefeet/1440min=0.001388 acrefeet/min
To know the number of gallons in a acrefeet we have to divide 450 by 0.001388
[tex]\frac{\frac{450gallons}{\min}}{\frac{0.001388\text{acreft}}{\min }}=324,207.5\text{ gallons per acreft}[/tex]