mphasis - a mixture of alcohol and water contains 10 water how much of alcohol will be added to 40 litres of mixture to reduce this water level to 4 - skillgun

Total Quantity of mixture is 40 litres.
Mixture has 10% of water.
Amount of water in the mixture = 10% of 40 litres = 10 x 40/100 = 4 litres ...(1) Assume the quantity of alcohol be x to make concentration of 4 litres of water to 4%.
After adding x litres of alcohol, the quantity of mixture becomes 40+x litres.
Quantity of water in new mixture = 4 litres
Total quantity of mixture after the addition of x litres of alcohol = 40+x litres
Percentage of water in mixture = 4% = (quantity of water / quantity of mixture) x100% = (4 / 40+x) * 100%
Or 4 = (4/40+x) * 100
Or 40+x = 100
Or x = 60