Gold is 19 times as heavy as water and copper is 9 times as heavy as water. In what ratio should these be mixed to get an alloy 15 times as heavy as water?

Question: Gold is 19 times as heavy as water and copper is 9 times as heavy as water. In what ratio should these be mixed to get an alloy 15 times as heavy as water?

Solution: Let Gold is 19x times as heavy as water and copper is 9y times as heavy as water.

Now,
→ 19x+ 9y = 15(x+y)
→ 19x+ 9y = 15 x+ 15y
→ 4x= 6y
→ x:y =6:4
→ x:y = 3:2