Mathematics
The mean of the following distribution is 50 and the frequency of the class-interval 20-40 is m, find the value of m.
| Class-interval | Frequency |
|---|---|
| 0-20 | 17 |
| 20-40 | m |
| 40-60 | 32 |
| 60-80 | 24 |
| 80-100 | 19 |
Statistics
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Answer
| Class-interval | Class-mark (x) | Frequency (f) | fx |
|---|---|---|---|
| 0-20 | 10 | 17 | 170 |
| 20-40 | 30 | m | 30m |
| 40-60 | 50 | 32 | 1600 |
| 60-80 | 70 | 24 | 1680 |
| 80-100 | 90 | 19 | 1710 |
| Total | Σf = 92 + m | Σfx = 5160 + 30m |
Given,
Mean = 50
⇒ 5160 + 30m = 50(92 + m)
⇒ 5160 + 30m = 4600 + 50m
⇒ 50m - 30m = 5160 - 4600
⇒ 20m = 560
⇒ m = = 28.
Hence, m = 28.
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