The average marks of 13 students are 67. If the average marks of the first seven students are 61 and the average marks of the last seven students are 65, what are the marks of the seventh student?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 11.
Total marks for all 13 students = 13 × 67 = 871
Total marks for the first seven students = 7 × 61 = 427
Total marks for the last seven students = 7 × 65 = 455
Marks of the seventh student = (427 + 455) - 871 = 11