Question

Vijay purchased two different kinds of alcohol. In the first mixture the ratio of alcohol to water is 3 : 4 and in the second mixture it is 5 : 6. If he mixes the two given mixtures and makes a third mixture of 18 litres in which the ratio of alcohol to water is 4 : 5, the quantity of the first mixture (whose ratio is 3 : 4) that is required to make 18 litres of the third kind of mixture is

• A. 6
• B. 7
• C. 8
• D. 9

Answer 1

Answer: (B)

7

Answer 2

By using allegation method,

Ratio of first mixture to second mixture mixed in third mixture,

⇒ $\frac{1}{99}:\frac{1}{66}$

⇒ $\frac{1}{11}:\frac{1}{7}$

⇒ $7:11$

Required quantity,

⇒ $\frac{7}{18}×18=7$

Hence, option B is the correct answer.The correct option is (B): 7