Question 13607
think of "before" and "after"


before --> got 50 litres of 60% and x litres of 30%.
after --> got (50+x) litres of 35%.


Just looking at this, the final solution is very close to the 30% solution, so there must be a lot of the 30%, to "drag" the concentration down from 60%. So i am looking for a common sense answer that is a lot more than 50 litres.


So,
(50*0.60) + (x*0.30) = (50+x)*0.35
30 + 0.3x = 17.5 + 0.35x
0.05x = 12.5
--> x = 250 litres.


jon.