SOLUTION: How many gallons of a 3% salt solution must be mixed with 30 gallons of a 9% solution to obtain a 6% solution?

Question 414226: How many gallons of a 3% salt solution must be mixed with 30 gallons of a 9% solution to obtain a 6% solution?
Answer by dnanos(83) (Show Source): You can put this solution on YOUR website!
We need,
X gallons 3%
and
30 gallons 9%
to obtain,
30+x gallons 6%
so
because the pure salt weight before and after mixing remains equal
we have the following equation.
(3/100)*x+ (9/100)*30=(6/100)*(30+x)
multiply by 100
3x+9*30=6(30+x)
3x+270=180+6x
3x-6x=180-270
-3x=-90
3x=90
3x/3=90/3
x=30
So we need 30 gallons of 3% ...
RELATED QUESTIONS
How many gallons of a 3% salt solution must be mixed with 30 gallons of a 9% solution to... (answered by mananth)

How many gallons of a 12% salt solution must be mixed with 6 gallons of a 20% salt... (answered by checkley77)

How many gallons of a 14%-salt solution must be mixed with 6 gallons of a 21%-salt... (answered by robertb,Tatiana_Stebko)

How many gallons of a 10%-salt solution must be mixed with 6 gallons of a 22%-salt... (answered by Tatiana_Stebko)

How many gallons of a 12%-salt solution must be mixed with 6 gallons of a 21%-salt... (answered by Maths68)

How many gallons of a 13%-salt solution must be mixed with 6 gallons of a 24%-salt... (answered by stanbon)

how many gallons of a 12%- salt solution must be mixed with 6 gallons of a 20%-salt... (answered by ewatrrr)

How many gallons of a 12%-salt solution must be mixed with 6 gallons of a 20%-salt... (answered by Theo)

How many gallons of a 12%-salt solution must be mixed with 6 gallons of a 20%-salt... (answered by josgarithmetic)