An alloy of copper and zinc contains copper and zinc in the ratio 6 : 4. Another alloy of copper and zinc contains copper and zinc in the ratio 3 : 7. In what ratio should the two alloys be mixed so that the resultant alloy contains equal proportions of copper and zinc?
Select the correct option.
A) 12 : 1 B) 1 : 2 C) 4 : 1 D) 2 : 5 E) 2 : 6
Let Alloy_1 be x units, and let Alloy_2 be y units.   So, fraction of copper in Alloy_1 = 6x/10, and fraction of zinc in Alloy_1 = 4x/10   Similarly, fraction of copper in Alloy_2 = 3y/10, and fraction of zinc in Alloy_2 = 7y/10.   Mixing them, we get   copper = 6x/10 +3y/10; zinc = 4x/10 + 7y/10   So, 6x+3y = 4x+7y   -&gt; 2x = 4y   -&gt; x/y =2/4 = 1/2   So, they must be mixed in the ratio 1 : 2   Answer : 1 : 2
<result>B</result>
An alloy of copper and zinc contains copper and zinc in the ratio 6 : 4. Another alloy of copper and zinc contains copper and zinc in the ratio 3 : 7. In what ratio should the two alloys be mixed so that the resultant alloy contains equal proportions of copper and zinc?