Heinz produces tomato puree by boiling tomato juice. Tomato puree has 20% water whereas tomato juice has 90% water.How many litres of tomato puree will be obtained from 20 litres of tomato juice ?

Answer: Option C

20 litres juice contain 10% Tomato, i.e.
20L juice = $$\frac{20\times 10}{100}$$  = 2L Tomato
Tomato puree contains 80% of water and 20% tomato.
This 80% tomato = 2L (which is contained by 100 puree)
So, Now this 2 L Consist 80% in puree
Thus, total puree will be $$\frac{2}{.8}=2.5\text{L}$$