How much would 500 gallons of water weigh if there was 250 pounds of salt added to it?

Answer 1

500 gallons of pure water weigh 4,172.6 pounds (rounded)

With 250 pounds of salt added, the mixture had better weigh 4,172.6 + 250 = 4,422.6 pounds,

or else mass has disappeared, which is a no-no.

Answer 2

The weight of 500 gallons of water is approximately 4,168 pounds. When adding 250 pounds of salt to it, the total weight would be 4,418 pounds.