Mathematics
The mean of the following distribution is 50. Find the unknown frequency.
| Class Interval | Frequency |
|---|---|
| 0 - 20 | 6 |
| 20 - 40 | f |
| 40 - 60 | 8 |
| 60 - 80 | 12 |
| 80 - 100 | 8 |
Measures of Central Tendency
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Answer
| Class Interval | Class mark (xi) | Frequency (fi) | fixi |
|---|---|---|---|
| 0 - 20 | 10 | 6 | 60 |
| 20 - 40 | 30 | f | 30f |
| 40 - 60 | 50 | 8 | 400 |
| 60 - 80 | 70 | 12 | 840 |
| 80 - 100 | 90 | 8 | 720 |
| Total | Σfi = 34 + f | Σfixi = 2020 + 30f |
By formula,
Mean =
Substituting values we get :
Hence, the value of f = 16.
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