Step 1 :The problem involves Mr. Jackson filling his family's pool with a hose that has a flow rate of 15 gallons per minute. It takes him 120 minutes to fill the 1,800-gallon pool. The function $V(t)$ represents the volume of water in the pool, in gallons, $t$ minutes after Mr. Jackson starts filling it.
Step 2 :The domain of a function is the set of all possible input values. In this case, the input value is the time in minutes.
Step 3 :Since Mr. Jackson starts filling the pool at time 0 and stops at 120 minutes, the domain of the function $V(t)$ should be all real numbers from 0 to 120.
Step 4 :This is because time is a continuous variable and can take any value in this interval.
Step 5 :\(\boxed{\text{The domain of } V(t) \text{ is all real numbers from 0 to 120.}}\)