Question 635359
Solution A
Amount=20 gallons
Concentration =15%=0.15


Solution B
Amount=x gallons
Concentration =0%=0 (Pure Water)


Mixture
Amount=(20+x)gallons
Concentration =12%=0.12

(Amount of Solution A)(Concentration of Solution B)+(Amount of Solution B)(Concentration of Solution A)=(Amount of Mixture)(Concentration of Mixture
(20)(0.15)+(x)(0)=(20+x)(0.12)
3+0=2.4+0.12x
3-2.4=0.12x
0.6=0.12x
0.6/0.12=0.12x/0.12
5=x
x=5


A 20-gallon salt-water solution contains 15% pure salt.  5 gallons of water should be added to make a new solution that is only 12% salt.