A zinc-copper alloy with 3 kg of pure zinc would contain 80% of zinc. The alloy with 2 kg of 80% zinc alloy contains 64% of zinc. Calculate the weight and percentage of zinc in the zinc-copper alloy.	Choose one:	A) 2.4 kg or 80%	B) 1.4 kg or 88%	C) 3.4 kg or 60%	D) 7.4 kg or 18%	E) 0.8 kg or 45.7%
Right Answer 0.8 kg or 45.7%xplanation:   x : 3   y : 100   80   20 : 80 – y   (80-y)/3 = 20/x = ………..(1)   In the second case,   x 2   y 80   64   16 64-y   Therefore (64-y)/2 = 16/x ………..(2)   Dividing (1) and (2)   =   640 – 8y = 960 – 15y   7y = 320   y = 45.7   x = 60/(80-45.7) = 60/34.3 = 1.75 kg   Quantity of zinc in x = 45.7% of x   = 0.457 1.75   = 0.799=0.8 kg   Weight and percentage of zinc is 0.8 kg or 45.7%   0.8 kg or 45.7%
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A zinc-copper alloy with 3 kg of pure zinc would contain 80% of zinc. The alloy with 2 kg of 80% zinc alloy contains 64% of zinc. Calculate the weight and percentage of zinc in the zinc-copper alloy.