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?
Σx/n = mean
for 19 students Σx = 19 * 14 = 266
(266 + x)/20 = 15
Solve for x.
-231
To find the mark on the missing paper, we can use the concept of averages.
We know that the average mark for 20 students is 15. This means that the total sum of the marks for all 20 students is 20 * 15 = 300.
However, before writing the marks in her mark book, the teacher loses 1 paper. So now we have only 19 marks remaining.
The average mark for the 19 remaining students is given as 14. This means that the total sum of the marks for the 19 students is 19 * 14 = 266.
To find the mark on the missing paper, we need to subtract the total sum of the 19 marks from the initial total sum of all 20 marks.
Therefore, the mark on the missing paper is 300 - 266 = 34.