An alloy weighing 60 ounces is 20 percent copper. How many ounces of copper must be added to create an alloy that is 60 percent copper?	Select:  A) 40  B) 50  C) 60  D) 70  E) 80
An alloy of 60oz which is 20% copper means there is 12 oz of gold. To get to an alloy that is 60% copper, let's use this expression: (12 + x)/(60 + x) = 0.60 with x representing the amount of pure copper that must be added to get to 60%. The expression we are using represents the new total weight of pure copper over the new total weight of the alloy and this fraction should represent 60% or 0.6. you will see that 60 is the correct answer, as  72/120= 
<gadget id="calculator"> 72/120</gadget>
<output>3/5 = around 0.6</output>
0.6   60hoose 60
<result>C</result>
An alloy weighing 60 ounces is 20 percent copper. How many ounces of copper must be added to create an alloy that is 60 percent copper?