Question 746137
The problem can be solved using the method of alligation.


Let S1 denote the 15% acid solution.


Let S2 denote the 25% acid solution.


Then 25-20=5 and 20-15=5


Therefore, the ratio of S1/S2=1/1


Since there are 2 parts of mixture for every 1 part of S1 (WLOG), we have the following relation:


S1=(1/2)(80)= 40 L (Answer)


S2=80-40= 40 L (Answer)