Question

Sharabi Chand 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 first mixture (whose ratio is 3: 4) required to make the 18 litres of the third kind of mixture is :

• A. 6
• B. 7
• C. 8
• D. 9

Answer 1

The correct option is B 7

The fraction of alcohol in the different mixtures is as follows
First mixture $\frac{3}{7}=\frac{297}{693}$
Second mixture $\frac{5}{11}=\frac{315}{693}$
Final mixture $\frac{4}{9}=\frac{308}{693}$
Therefore

Hence the ratio of the first mixture to the second mixture is 7 :11. Thus he has to mix 7 litres of the first type of alcohol to make 18 litres of the required mixture.