Thirty pounds of a salt-water solution contains fifteen percent salt. How much water must be added to weaken the solution to ten percent salt?
a 1.5 lb
b 3 lb
c 15 lb
_____ The 30 pounds of 15% solution contains 30*.15 = 4.5 lb of salt. In order for that amount of salt to comprise a 10% solution, 4.5/0.10 = 45 lb of solution are needed. 45 -30 = 15 lb of water must be added.
