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Question
The following table gives the heights of plants in centimeter. If the mean height of plants is 60.95 cm; find the value of 'f'.
| Height (cm) | 50 | 55 | 58 | 60 | 65 | 70 | 71 |
| No. of plants | 2 | 4 | 10 | f | 5 | 4 | 3 |
Solution
| Height (cm) xi |
No. of plants fi |
fixi |
| 50 | 2 | 100 |
| 55 | 4 | 220 |
| 58 | 10 | 580 |
| 60 | f | 60f |
| 65 | 5 | 325 |
| 70 | 4 | 280 |
| 71 | 3 | 213 |
| Total | 28 + f | 1718 + 60f |
Mean = 60.95
`=> (1718 + 60f)/28 + f = 60.95`
`=>` 1718 + 60f = 60.95 (28 + f)
`=>` 1718 + 60f = 1706.6 = 60.95f
`=>` (60.95 – 60)f = 1718.0 – 1706.6
`=>` 0.95f = 11.4
`=> f = 11.4/0.95`
`=>` f = 12
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