The average marks of 12 students in a mathematics test are 63.5. Later, it was found that one student’s score was misread as 56 instead of 65. After correcting this error, another student’s marks were removed for being invalid, and the average of the remaining 11 students rose to 64.2. Find the marks of the student whose score was removed.
Show answer & explanation
Correct answer: C
Explanation
Given:
Number of students = 12
Average marks = 63.5
Correct marks of one student = 65 (56 was taken by mistake)
Number of students at the end = 11
New average = 64.2
By the formula:
Total marks = Average × Number of students
Incorrect total marks = 63.5 × 12 = 762
Correct total marks = 762 − 56 + 65 = 771
Total marks of 11 students = 64.2 × 11 = 706.2
Marks of the excluded student = 771 − 706.2 = 64.8