The grade point average of one third of the classroom is 45; the grade point average of the rest is 60. What is the grade point average of the whole class?  Choose one
A) 54  B) 55  C) 60  D) 65  E) 70

Rationale: let n = total students in class total points for 1 / 3 class = 45 n / 3 = 15 n total points for 2 / 3 class = 60 * 2 n / 3 = 40 n total points for whole class = 15 n + 40 n = 55 n 63 n total class points / n total students = 55 grade point average for total class answer : b
Answer: B