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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 eight paper will be:

Solution

✅ Correct Option: 1

The total papers = 15

Average marks of all 15 papers = 45

Average marks of first 8 papers (papers 1 to 8) = 48

Average marks of last 8 papers (papers 8 to 15) = 40


Total marks of all 15 papers:

Total=45×15\text{Total} = 45 \times 15

Total=675\text{Total} = 675


Total marks of first 8 papers:

Total=48×8\text{Total} = 48 \times 8

Total=384\text{Total} = 384


Total marks of last 8 papers:

Total=40×8\text{Total} = 40 \times 8

Total=320\text{Total} = 320


The 8th paper appears in both the first 8 papers and the last 8 papers.

Adding the totals of first 8 and last 8 papers:

384+320=704384 + 320 = 704

The difference between this sum and the actual total:

704−675=29704 - 675 = 29

This difference represents the marks of the 8th paper, which was counted twice.

Therefore, the marks of the 8th paper = 29

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