The ratio, by volume, of acid to base to water in a certain solution is 4:15:20. The solution is altered so that the ratio of acid to base is 3:5 and the ratio of acid to water remains same. If the solution initially contained 30mm of base, what is the minimum amount of water that could be added in the second phase?
A) 18 B) 36 C) 50 D) 60 E) 90

* Now A:B:W = 4:15:20 ...With initial 30 ml base...Hence Intial sol'n - 8 : 30 : 40....40 ml of water present.
* New ratio's - A:B - 3:5 & A:W = 4:20 i.e. 1:5....Hence the combined ratio - 3:5:15.. With 30 ml of base still in the new altered solution.....Hence 18: 30 : 90....
* Water added - 90 - 40 = 50...

Ans C