Some pupils took a Math mock exam. Their average score was 78.7 marks. One of the pupils' scores was wrongly recorded as 79 marks instead of 97 marks. As a result, the average score was calculated as 77.5 marks. How many pupils sat for the mock exam?
|
If that pupil's score was 97 |
If that pupil's score was 79 |
Number of pupils |
1 u |
1 u |
Average score |
78.7 |
77.5 |
Total score |
78.7 u |
77.5 u |
Difference in the scores due to being wrongly recorded
= 97 - 79
= 18
Difference in total scores of the pupils is due to the difference in the wrongly recorded score.
78.7 u - 77.5 u = 18
1.2 u = 18
1 u = 18 ÷ 1.2 = 15
Number of pupils = 15
Answer(s): 15