Question

A 40 litre of mixture of milk and water contain 10% water then how much water must be added to make the concentration of water 20%....................plz give me the answer as soon as possible .

Answer 1

10 percent of 40 is 4 lites of water
now
$\frac{20}{100} \times (40 + x) = 4 + x \\ 40 + x = 20 + 5x \\ x = 5$
5 litres of water more should be added