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The average of marks of 14 student was calculated as 71. But it was later found that the marks of one student had been wrongly entered as 42 instead of 56 and of another as 74 instead of 32. The correct average is :
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- 67
- 68
- 69
- 71
- 67
Correct Option: C
According to question,
The average of marks of 14 student was calculated as 71.
Total marks = 71 × 14 = 994
Correct total marks = 994 + (56 – 42) + (32 – 74)
Correct total marks = 994 + 14 – 42 = 966
| ∴ Required average = | = 69 | |
| 14 |
Second method to solve this question with the help of given formula :
Here n = 14, m = 71 , a = 56, b = 42 , p = 32, q = 74
| Correct Average = m + | |
| n |
| Correct Average = 71 + | |
| 14 |
| Correct Average = 71 - | |
| 14 |
Correct Average = 71 – 2 = 69
