If 15 students in a class average 75% on an exam and 10 students average 90% on the same exam, what is the average in percent for all 25 students?	Choose the correct choice.
A) 80 %
B) 81 %
C) 82 %
D) 83 %
E) 84 %

Rationale: "( 15 * 75 + 10 * 90 ) / 25 = 81 % the answer is b ."
Answer: B