Management Aptitude Test Dec 2012 Paper

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 L 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 L of the third kind of mixture is