Answer:
You will add water after 4 days.
Step-by-step explanation:
Initial volume = 55 gallons
Final volume 49 gallons
Difference in volumes = 55 - 49 = 6 gallons
Rate of evaporate = 1.5 gallons per day
Number of days = n
Thus, in n days, 6 gallons of water evaporate, so
[tex]1.5\cdot n=6\\ \\15n=60\ \ [\text{Multiply by 10}]\\ \\n=\dfrac{60}{15}\\ \\n=4\ days[/tex]
You will add water after 4 days.