A zinc-copper alloy with 6 kg of pure zinc would contain 90% of zinc. The alloy with 4 kg of 90% zinc alloy contains 84% of zinc. Calculate the weight and percentage of zinc in the zinc-copper alloy.
Choices:
A) 2.4 kg or 80%  B) 4.8 kg or 80%  C) 3.4 kg or 60%  D) 7.4 kg or 18%  E) 1.4 kg or 60%
Right Answer Explanation:   x : 6   y : 100   90   10 : 90 – y   (90-y)/6 = 10/x = ………..(1)   In the second case,   x 4   y 90   84   6 84-y   Therefore (84-y)/4 = 6/x ………..(2)   Dividing (1) and (2)   =   540 – 6y = 1260 – 15y   9y = 720   y = 80   x = 60/(90-80) = 60/10= 
<gadget id="calculator">60/10</gadget>
<output>6</output>
6 kg   Quantity of zinc in x= 80% of x   = 0.8 6   = 4.8 kg   Weight and percentage of zinc is 4.8 kg or 80%   4.8 kg or 80%
<result>B</result>
A zinc-copper alloy with 6 kg of pure zinc would contain 90% of zinc. The alloy with 4 kg of 90% zinc alloy contains 84% of zinc. Calculate the weight and percentage of zinc in the zinc-copper alloy.