Question 79617

Let x=number of liters of acid/water mixture added to the 5 liters of pure acid.

Then0.90x=amount of pure water added to the 5 liters of pure acid

Now we know that the amount of pure water added to the 5 liters of pure acid equals the amount of pure water in the final mixture.  So our equation to solve is:

0.90x=0.40(5+x)  get rid of parens

0.90x=2+0.40x  subtract 0.40x from each side

0.90x-0.40x=2+0.40x-0.40x  collect like terms

0.50x=2  divide both sides by 0.50

x=4 liters------------------amount of mixture added to the pure acid

0.90x=0.90*4=3.6 liters---------------------amount of pure water in final mixture

CK.

0.40(5+4)=3.6

3.6=3.6

Hope this helps----ptaylor