The average marks of 15 students in a science laboratory practical were 64. Later, it was found that the mark of one student was wrongly taken as 58 instead of 85. After correcting the mistake, the average increases. Now, a new student joins whose marks are 10% more than the new average. What is the final average of the group?
Show answer & explanation
Correct answer: B
Explanation
Given:
Number of students = 15
Average marks = 64
Incorrect marks = 58
Correct marks = 85
Incorrect total marks = 15 × 64 = 960
Total marks after correction = 960 − 58 + 85 = 987
New average = 987 / 15 = 65.8
New student's marks = 65.8 × 1.10 = 72.38
New total marks = 987 + 72.38 = 1059.38
Total students = 16
Final average = 1059.38 / 16 = 66.21