Question 67414
Let x= amount of 80% 
Then 600-x= amount of 40%

Now we know that the amount of pure disinfectant in the 80% mixture (.8x) plus the amount of pure disinfectant in the 40% misture .4(600-x) must equal the amount of pure disinfectant in the final solution .5(600).  So our equation to solve is:


.8x+.4(600-x)=.5(600)  simplifying we get

.8x+240-.4x=300  subtract 240 from both sides and collect like terms:

.4x=60
x=150  ml -----------------amount of 80% solution

600-x=600-150=450 ml-----------amount of 40% solution

CK

450(.4)+150(.8)=.5(600)
180+120=300
300=300


Hope this helps----ptaylor