Mathematics
The following distribution shows the daily pocket allowance of children of a locality. The mean pocket allowance is ₹ 18. Find the missing frequency f.
| Daily pocket allowance (in ₹) | Number of children |
|---|---|
| 11 - 13 | 7 |
| 13 - 15 | 6 |
| 15 - 17 | 9 |
| 17 - 19 | 13 |
| 19 - 21 | f |
| 21 - 23 | 5 |
| 23 - 25 | 4 |
Statistics
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Answer
By formula,
Class mark =
| Daily pocket allowance (in ₹) | Number of children ( fi) | Class mark (xi) | fixi |
|---|---|---|---|
| 11 - 13 | 7 | 12 | 84 |
| 13 - 15 | 6 | 14 | 84 |
| 15 - 17 | 9 | 16 | 144 |
| 17 - 19 | 13 | 18 | 234 |
| 19 - 21 | f | 20 | 20f |
| 21 - 23 | 5 | 22 | 110 |
| 23 - 25 | 4 | 24 | 96 |
| Total | Σfi = 44 + f | Σfixi = 752 + 20f |
By formula,
Mean =
Substituting values we get :
Hence, f = 20.
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