ten litres of a mixture contain 60% of alcohol and 40% of water by volume.How many litres of water should be added so that it contains 30% of alcohol by volume?
+130511 So...putting everything in terms of % of water, we want the final mix to contain 70% water....note that pure water = 100% = 1
So we have
10*.40 + 1x = (x + 10)*.70 simplify
4 + x = .7x + 7 subtract 4, .7x from both sides
3x = .3x divide both sides by .3
3/.3 = x = 10 litres
+130511 So...putting everything in terms of % of water, we want the final mix to contain 70% water....note that pure water = 100% = 1
So we have
10*.40 + 1x = (x + 10)*.70 simplify
4 + x = .7x + 7 subtract 4, .7x from both sides
3x = .3x divide both sides by .3
3/.3 = x = 10 litres
