A dessert recipe calls for 50% melted chocolate and 50% raspberry puree to make a particular sauce. A chef accidentally makes 15 cups of the sauce with 30% melted chocolate and 70% raspberry puree instead. How many cups of the sauce does he need to remove and replace with pure melted chocolate to make the sauce the proper 50% of each?  Answers.
A) 1.5
B) 2.14
C) 3
D) 4.5
E) 5
Yes, we assume that the mix is homogeneous. Otherwise, we will not be able to solve the question.   You have 15 cups of sauce with 30% chocolate. You also have unlimited amount of pure chocolate sauce. Now you need to mix these two in such a way that you get total 15 cups of sauce with 50% chocolate.   Using scale method:   w1/w2 = (100 - 50)/(50 - 30) = 5/2   w1 - Amount of 30% chocolate sauce   w2 - Amount of pure chocolate sauce   So for every 5/2 cups of 30% chocolate sauce, we need 2 cup of pure chocolate sauce. This will give us 7 cups of 50% chocolate sauce. But we need 15 cups of 50% chocolate sauce.   So we need to mix 5*15/7 = 12.5 cups of 40% chocolate sauce with 1*15/7 = 2.14 cups of pure chocolate sauce.   Answer (2.14)
<result>B</result>
A dessert recipe calls for 50% melted chocolate and 50% raspberry puree to make a particular sauce. A chef accidentally makes 15 cups of the sauce with 30% melted chocolate and 70% raspberry puree instead. How many cups of the sauce does he need to remove and replace with pure melted chocolate to make the sauce the proper 50% of each?