Question 619960: how many liters each of a 65% acid solution and a 30% acid solution must be used to make 70 liters of a 60% acid solution? Answer by dragonwalker(73) (Show Source):
You can put this solution on YOUR website! You first want to look at each solution's difference from the desired concentration so:
for the 65% acid solution this is +5 different from the desired 60%
for the 30% acid solution this is -30 different from the desired 60%
So in order for this to balance look at the one that has a bigger difference, in this case the 30% with a difference of -30
the difference of the 65% acid solution is only +5 so how many times is this smaller than the other difference of 30? 30/5 =6
So for every one unit of the 30% solution you need to add 6 units of the solution that makes less of a difference (65%). This evens the changes out. To find out how much of each you know that we will be adding 6 times the 65% solution than the 30% solution so let us word it like this:
amount of 30% + amount of 65% = the total volume
we know the total volume will be 70 liters and we shall call the amount of 30% solution added 'x'
So:
x + 6x = 70
(as if x of 30% sol. we know that six times this i.e. 6x of the 65% sol. is used)
So:
solve for x
7x = 70
divide both sides by 7 to find x:
7x/7 = 70/7
x = 10
so we know that 10 liters of 30% solution is needed. Therefore 6 times this amount (i.e. 60 liters) of 65% solution is also needed.
To check add these volumes together = 10+60 = 70!!!
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