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?
Let the quantity of the wine in the cask originally be x litres Then, quantity of wine left in cask after 4 operations = x 1 - 8 x 4 litres ? x 1 - 8 x 4 x = 16 81 ? 1 - 8 x 4 = 2 3 4 ? x = 24