Some pupils took a Math mock exam. Their average score was 78.4 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 77.2 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 |
78.4 |
77.2 |
| Total score |
78.4 u |
77.2 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.
78.4 u - 77.2 u = 18
1.2 u = 18
1 u = 18 ÷ 1.2 = 15
Number of pupils = 15
Answer(s): 15
