SOLUTION: 0. How many gallons of rocket fuel containing 80% liquid oxygen must be mixed with 250 gallons containing 40% liquid oxygen to produce a mixture containing 70% liquid oxygen?

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Question 961453: 0. How many gallons of rocket fuel containing 80% liquid oxygen must be mixed with 250 gallons containing 40% liquid oxygen to produce a mixture containing 70% liquid oxygen?
Answer by addingup(3677) About Me  (Show Source):
You can put this solution on YOUR website!
We'll call the unknown quantity x, and we have:
how many gallons of 80%: .8x, since we don't know how many gallons
mixed with 250 gall of 40%: .40*250
and we want a mix at 70%. The mix will include the .8x and the .4*250 Like this:
.8x+.4*250= .7x+.7*250 Multiply on both sides of the equation:
.8x+100= .7x+175 Subtract 100 on both sides
.8x= .7x+75 Subtract .7 on both sides
.1x= 75 Divide both sides by .1
x= 750
You need 750 gallon of fuel at 80% to mix with the 250 gallon at 40% in order to get a mixture at 70% liquid oxygen.