The teacher collected the test papers of 20 students and found that their average mark was 15. Before she wrote the marks in her mark book, she lost 1 paper. Find the mark for the missing paper, she worked out the average mark for the 19 students was 14. What was the mark on the missing paper?

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  1. Σx/n = mean

    for 19 students Σx = 19 * 14 = 266

    (266 + x)/20 = 15

    Solve for x.

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  2. -231

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