An alloy of copper and zinc contains copper and zinc in the ratio 5 : 3. Another alloy of copper and zinc contains copper and zinc in the ratio 1 : 7. In what ratio should the two alloys be mixed so that the resultant alloy contains equal proportions of copper and zinc? Choose the correct choice:
A) 1 : 5  B) 7 : 3  C) 5 : 3  D) 3 : 1  E) 4 : 3
Alloy-1: Copper: Zinc = 5:3, Let Quantity = x   i.e. Copper in Alloy-1 = [5/(5+3)]*x = (5/8)x   and Zinc in Alloy-1 = [3/(5+3)]*x = (3/8)x   Alloy-2: Copper: Zinc = 1:7, Let Quantity = y   i.e. Copper in Alloy-2 = [1/(1+7)]*y = (1/8)y   and Zinc in Alloy-1 = [7/(1+7)]*y = (7/8)y   After Combining the two alloys   Copper = (5/8)x + (1/8)y   Zinc = (3/8)x + (7/8)y   Now, (5x + y)/8 = (3x + 7y)/8   i.e. 2x = 6y   i.e. x = 3y   i.e. x/y = 3/1   Answer: option 3 : 1
<result>D</result>
An alloy of copper and zinc contains copper and zinc in the ratio 5 : 3. Another alloy of copper and zinc contains copper and zinc in the ratio 1 : 7. In what ratio should the two alloys be mixed so that the resultant alloy contains equal proportions of copper and zinc?