The ratio of acid and water in solution A and solution B is 7: 8 and 9: 11, respectively. 3 litres of solutionA is mixed with 4 litres of solution B and 1 litre water is also added to it. What is the percentage of acid inthe resulting solution?

Correct option is A

​Given :

In solution A, Acid : Water = 7 : 8

In solution B, Acid : Water = 9 : 11

3 litres of solution A

4 litres of solution B

1 litre pure water added

Solution :

Acid in solution A

Total parts = 7 + 8 = 15

Acid in A:
3 $$\times \frac{7}{15} = \frac{21}{15} = 1.4 \text{ litres}$$​​
Acid in solution B

Total parts = 9 + 11 = 20

Acid in B:
​$$4 \times \frac{9}{20} = \frac{36}{20} = 1.8 \text{ litres}$$​​
Total acid

1.4 + 1.8 = 3.2 litres
Total solution volume

3 + 4 + 1 = 8 litres
Percentage of acid

​$$\frac{3.2}{8} \times 10$$​0 = 40%
Percentage of acid in the resulting solution = 40%