how many gallons?

Question

a fuel distributor has 120 000 gallons of fuel with a .9% sulfer content, which exceeds pollution control standards of .8% sulfur content. how many gallons of fuel oil with a .3% sulfur content must be added to the 120 000 gallons to obtain fuel oil that will comply with the pollution control standards?

Answer 1

Let x be gallons of .3% sulfur fuel oil added. Then the amount of sulfur is 120000(.009)+.003x.

the percentage of sulfur is (120000(.009)+.003x)/(120000+x)=.008 to comply with pollution standards.

(120000(.009)+.003x)=.008(120000+x)

120*9+.003x=120*8+.008x

120=.005x

Solve for x.