Some pupils took a Math exam. Their average score was 70.5 marks. One of the pupils' scores was wrongly recorded as 78 marks instead of 87 marks. As a result, the average score was calculated as 70.3 marks. How many pupils sat for the exam?
|
If that pupil's score was 87 |
If that pupil's score was 78 |
Number of pupils |
1 u |
1 u |
Average score |
70.5 |
70.3 |
Total score |
70.5 u |
70.3 u |
Difference in the scores due to being wrongly recorded
= 87 - 78
= 9
Difference in total scores of the pupils is due to the difference in the wrongly recorded score.
70.5 u - 70.3 u = 9
0.2 u = 9
1 u = 9 ÷ 0.2 = 45
Number of pupils = 45
Answer(s): 45