Gold is 19 times as heavy as water and copper is 9 times heavy. In what ratio must these metals be mixed so that the mixture may be 15 times as heavy as water?	Choose the correct option:
A) 2 : 3 B) 3 : 2 C) 1 : 3 D) 2 : 1 E) none of these

Rationale: "? required ratio = 6 ? 4 = 3 : 2 answer b"
Answer: B