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प्रश्न
Find the mean of: all prime numbers between 20 and 40.
उत्तर
All prime numbers between 20 and 40 are 23, 29, 31, 37
Sum of these observations = 23+29 + 31 + 37 = 120 .
and, number of their observations = 4
∴ Required mean = `120/4 = 30`
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संबंधित प्रश्न
The contents of 100 match boxes were checked to determine the number of matches they contained.
| No. of matches | 35 | 36 | 37 | 38 | 39 | 40 | 41 |
| No. of boxes | 6 | 10 | 18 | 25 | 21 | 12 | 8 |
- Calculate, correct to one decimal place, the mean number of matches per box.
- Determine, how many extra matches would have to be added to the total contents of the 100 boxes to bring the mean up to exactly 39 matches.
The following are the marks obtained by 70 boys in a class test:
| Marks | No. of boys |
| 30 – 40 | 10 |
| 40 – 50 | 12 |
| 50 – 60 | 14 |
| 60 – 70 | 12 |
| 70 – 80 | 9 |
| 80 – 90 | 7 |
| 90 – 100 | 6 |
Calculate the mean by:
Step-deviation method
The mean of the following distribution is `21 1/7`. Find the value of ‘f’.
| C.I. | 0 – 10 | 10 – 20 | 20 – 30 | 30 – 40 | 40 – 50 |
| Frequency | 8 | 22 | 31 | f | 2 |
Find the mode of the following data:
7, 9, 8, 7, 7, 6, 8, 10, 7 and 6
The marks of 20 students in a test were as follows:
2, 6, 8, 9, 10, 11, 11, 12, 13, 13, 14, 14, 15, 15, 15, 16, 16, 18, 19 and 20.
Calculate:
- the mean
- the median
- the mode
Find the mode of the following:
20, 20, 30, 30, 30, 30, 35, 40, 40, 45, 45, 45, 50, 55, 60, 60, 60 ,65, 70, 70, 70
Find the median of the following:
25, 34, 31, 23, 22, 26, 35, 29, 20, 32
Find the mean of: 7, 10, 4 and 17
Find the mean of: 12, 9, 6,11 and 17
Find the mean of: 2.1, 4.5, 5.2, 7.1 and 9.3
