A solution contains acid and water in the ratio of 4 : 5. If 20% of the solution is replaced by water, then what will be the ratio of acid and water in the new solution?

16 : 29

Here,

Ratio of acid and water = 4 : 5

⇒ Let the total solution be 90 units, 

⇒  Amount of acid = 90 × \(\frac{4}{9}\) = 40 units 

⇒ Amount of water = 90 × \(\frac{5}{9}\) = 50 units 

⇒ 20% of the total solution is taken out = 90 × \(\frac{20}{100}\) = 18 units 

⇒ Acid and water will be taken out in 4 : 5 

⇒ Remaining amount of acid = 40 - 18 × \(\frac{4}{9}\) = 32

⇒ Remaining amount of water = 50 - 18 × \(\frac{5}{9}\) = 40

The amount taken out is replaced with water; 

So, new quantity of water = 40 +  18 = 58 

Therefore, The ratio of acid and water in the new solution = 32 : 58 = 16 : 29