Question

Rosamaria is setting up a 20-gallon saltwater fish tank that needs to have a salt content of 3.5%. If Rosamaria has water that has 2.5% salt and water that has 3.7% salt, how many gallons of the water with 3.7% salt content should Rosamaria use?

Answer 1

`3.33` gallons from 2.5% salty water and `16.67` gallons from 3.7% salty water, well mix, that is done Rosamaria!

Explanation:

Your mathematical expression is:

`(0.025*x)+(0.037(20-x))=0.035*20`

x stands for volume of water required from 2.5% salty water stock. When you get this amount, the rest (20-x) will be taken from 3.7% salty water stock.

Solve this question:

`0.025*x+0.74-0.037*x=0.70`

`0.74-0.70=0.012*x`

and x is

`x=0.04/0.012=3.33` gallons.

Take 3.33 gallons from 2.5% salty water stock and take `20-3.33=16.67` gallons from 3.7% salty water stock. Mix your water. Rosamaria finally gets 3.5% salty water of 20 gallons total. Well done!