Alligation or Mixture problems
From a vessel filled with alcohol 1/5 of its contents is removed and the vessel is then filled up with water. If this be done 5 times in succession, what proportion of the alcohol originally contained in the vessel will have been removed from it?
W 1 : A 1 W 2 : A 2 . . . . . W N : A N 2 : 3 4 : 5 5 : 7 W 1 W 1 + A 1 = 2 5 W 2 W 2 + A 2 = 4 9 W N W N + A N = 5 12 = 72/180 = 80/180 = 75/180 => 5 : 3 Therefore, the ratio is 5: 3