An alloy weighing 48 ounces is 25% gold. How many ounces of pure gold must be added to create an alloy that is 40% gold? Choose the correct choice from the following answers.
A) 15  B) 20  C) 12  D) 14  E) 7
An alloy of 48oz which is 25% gold means there is 12 oz of gold. To get to an alloy that is 40% gold, let's use this expression: (12 + x)/(48 + x) = 0.40 with x representing the amount of pure gold that must be added to get to 40%. The expression we are using represents the new total weight of pure gold over the new total weight of the alloy and this fraction should represent 40% or 0.4. you will see that 12 is the correct answer, as  24/60= 
<gadget id="calculator"> 24/60</gadget>
<output>2/5 = around 0.4</output>
0.4   12hoose 12
<result>C</result>
An alloy weighing 48 ounces is 25% gold. How many ounces of pure gold must be added to create an alloy that is 40% gold?