Some pupils took a Math mock exam. Their average score was 71.9 marks. One of the pupils' scores was wrongly recorded as 68 marks instead of 86 marks. As a result, the average score was calculated as 70.7 marks. How many pupils sat for the mock exam?
|
If that pupil's score was 86 |
If that pupil's score was 68 |
Number of pupils |
1 u |
1 u |
Average score |
71.9 |
70.7 |
Total score |
71.9 u |
70.7 u |
Difference in the scores due to being wrongly recorded
= 86 - 68
= 18
Difference in total scores of the pupils is due to the difference in the wrongly recorded score.
71.9 u - 70.7 u = 18
1.2 u = 18
1 u = 18 ÷ 1.2 = 15
Number of pupils = 15
Answer(s): 15