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Question
If the mean of the following data is 20.2, then find the value of p
| Marks | 10 | 15 | 20 | 25 | 30 |
| No. of students | 6 | 8 | p | 10 | 6 |
Solution
| Marks x |
No. of students f |
fx |
| 10 | 6 | 60 |
| 15 | 8 | 120 |
| 20 | p | 20p |
| 25 | 10 | 250 |
| 30 | 6 | 180 |
| `sumf` = 30 + p | `sumfx` = 610 + 20p |
`bar(x) = (sumfx)/(sumf)`
20.2 = `(610 + 20"p")/(30 + "p")`
610 + 20 p = 20.2 ...(30 + p)
610 + 20 p = 606 + 20.2 p
610 – 606 = 20.2 p – 20 p
4 = 0.2 p
p = `4/0.2`
= `(4 xx 10)/2`
= 20
The value of p = 20
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