Question

Maria is setting up a 20gal salt water fish tank. That needs to have a salt content of 3.5% . if she has water with 2.5% salt and water with 3.7% salt. How many gallons of water with 3.7% salt content must she use????

Answer 1

x + y = 20   ---> x = 20 - y

2.5x + 3.7y = (3.5)(20) = 70

--> 2.5(20-y) + 3.7y = 70

--> 50 -2.5y +3.7y = 70

--> 1.2y = 20

--->  y = 16.66

Answer: 16.66 gallons