Question 13722
before and after is the secret, so...


BEFORE:
4*0.20 of the solution
1*1.00 of the concentrate (1.00 meaning 100% concentrate)


AFTER:
5*x of the new solution


--> 4*0.2 + 1 = 5x
0.8 + 1 = 5x
5x = 1.8
--> x = 0.36


so new concentration is 36%


jon.