Question

One litre of water is added to 5 litres of 20% solution of alcohol and water. what is the final strength of alcohol?

Answer 1

20% of 5 L = 0.20×5 = 1 L 
The 5 L of 20% solution contains 1 L of alcohol. 

After adding 1 L, the 6 L contains 1 L of alcohol. 
1 L/6 L = 1/6 = 0.16666... ≅ 0.167 = 16.7%

Answer 2

Answer:

The final strength of the alcohol is 16.66%.

Explanation:

20 % of 5 L alcohol solution.

Volume of water = 4 L

Volume of alcohol = $5L\times \frac{20}{100}=1L$

After addition of 1 L of water in the solution.

Volume of the water becomes = 1 L+4 L= 5 L

Volume of solution = 6 L

Final strength of solution:

$\frac{1 L}{6L}\times 100=16.66\%$

The final strength of the alcohol is 16.66%.