The average height of 30 students in a class was calculated as 175 cm. It has later found that the height of one of the students in the class was incorrectly written as 151 cm whereas the actual height was 136 cm. What was the actual average height of the students in the class?  Choose one:
A) 174.5
B) 173.5
C) 172.5
D) 171.5
E) 170.5

Rationale: "the total height was 15 cm too much . the average height should be reduced by 15 cm / 30 = 0.5 cm the answer is a ."
Answer: A