The ratio of water and alcohol in two different containers is 2:3 and 4:5. In what ratio we are required to mix the mixtures of two containers in order to get the new mixture in which the ratio of alcohol and water be 7:5?

• A. 8:5
• B. 5:3
• C. 2:7
• D. 7:3

Answer: (B)

W 1 : A 1     W 2 : A 2     . . . . .   W N : A N   2 : 3                   4 : 5                    5 : 7    W 1 W 1 + A 1   =   2 5   W 2 W 2 + A 2 = 4 9     W N W N + A N   =   5 12 = 72/180 = 80/180 = 75/180                            =>     5   :   3   Therefore, the ratio is  5: 3