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 ? Select the correct option:
A) 3 : 2
B) 3 : 8
C) 5 : 7
D) 3 : 7
E) 3 : 6
Let us say, water weighs 1kg/1 liter. Then Gold weighs 19 kgs and copper weighs 9 kgs.   Assume x kgs of gold and y kgs of copper required to get the required alloy.   We use weighted average formula = Ax=n1.A1+n2.A2n1+n2Ax=n1.A1+n2.A2n1+n2   Therefore, 15=x.19+y.9x+y15=x.19+y.9x+y   15x + 15y = 19x + 9y   4x = 6y ⇒ x/y = 3 : 2   So Gold and Copper should be mixed in the ratio 3 : 2.   3 : 2nswer:3 : 2
<result>A</result>
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 ?