Two vessels contains equal number of mixtures milk and water in the ratio 3:2 and 4:1. Both the mixtures are now mixed thoroughly. Find the ratio of milk to water in the new mixture so obtained?
Choose the correct choice from the following options
A) 1 : 3 B) 9 : 13 C) 5 : 11 D) 7 : 3 E) 15 : 4

Rationale: "the ratio of milk and water in the new vessel is = ( 3 / 5 + 4 / 5 ) : ( 2 / 5 + 1 / 5 ) = 7 / 5 : 3 / 5 = 7 : 3 answer is d"
Answer: D