The average of marks of 15 papers is 45. The average of marks of the first 8 papers is 48 and that of the last 8 papers is 40. The marks of the eighth paper will be:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 29
Total marks = average × number of papers. The first 8 papers (1st to 8th) and the last 8 papers (8th to 15th) together count 16 papers, so the eighth paper is counted twice. The extra over the total of all 15 papers is the eighth paper’s marks.
Total of all 15 papers \(=15\times45=675\)
Total of the first 8 papers \(=8\times48=384\)
Total of the last 8 papers \(=8\times40=320\)
Marks of the eighth paper \(=384+320-675=29\)