If 15% of a class averages 100% on a test, 50% of the class averages 78% on the test, and the remainder of the class averages 63% on the test, what is the overall class average? (Round final answer to the nearest percent).  Choose one:
A) 76 % B) 77 % C) 78 % D) 79 % E) 80 %

Rationale: "this question is a weighted average question with a series of dependent variables . the remaining portion of the class represents 100 % - 15 % - 50 % = 35 % of the class converting the portions of the class population to decimal weights , we find : class average = 0.15 x 100 + 0.50 x 78 + 0.35 x 63 = 76.05 the class average ( rounded ) is 76 % final answer a ) 76 %"
Answer: A