# A vat contains 100 gallons of a 50% brine solution. What is the greatest amount of water that can be added if the salt content cannot drop below 25%?

In the original 100 gallons, 50% is brine. Hence, there is 100$/$2= 50 gallons of brine solution. For 50 gallons to be at minimum 25% of the total volume, total volume must be 50 x (100/25) = 200 gallons.