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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
Find the mean of the following distribution by step deviation method:
| Class Interval | 20-30 | 30-40 | 40-50 | 50-60 | 60-70 | 70-80 |
| Frequency | 10 | 6 | 8 | 12 | 5 | 9 |
The following table gives the age of 50 student of a class. Find the arithmetic mean of their ages.
| Age-years | 16 – 18 | 18 – 20 | 20 – 22 | 22 – 24 | 24 – 26 |
| No. of students | 2 | 7 | 21 | 17 | 3 |
A boy scored following marks in various class tests during a term; each test being marked out of 20.
15, 17, 16, 7, 10, 12, 14, 16, 19, 12 and 16
What are his median marks?
The marks of 200 students in a test were recorded as follows:
| Marks | No. of students |
| 10-19 | 7 |
| 20-29 | 11 |
| 30-39 | 20 |
| 40-49 | 46 |
| 50-59 | 57 |
| 60-69 | 37 |
| 70-79 | 15 |
| 80-89 | 7 |
Construct the cumulative frequency table. Drew the ogive and use it too find:
(1) the median and
(2) the number of student who score more than 35% marks.
Find the mean of first 12 even numbers.
The mean of a certain number of observations is 32. Find the resulting mean, if the observation is, multiplied by 2
The mean of 5 numbers is 27. If one new number is included, the new mean is 25. Find the included number.
If the mean of x, x + 2, x + 4, x + 6 and x + 8 is 13, find the value of x. Sum of data.
Find the median of 17, 23, 36, 12, 18, 23, 40 and 20
The marks of 200 students in a test were recorded as follows:
| Marks % |
0-10 | 10-20 | 20-30 | 30-40 | 40-50 | 50-60 | 60-70 | 70-80 | 80-90 | 90-100 |
| No. of students |
5 | 7 | 11 | 20 | 40 | 52 | 36 | 15 | 9 | 5 |
Using graph sheet draw ogive for the given data and use it to find the,
- median,
- number of students who obtained more than 65% marks
- number of students who did not pass, if the pass percentage was 35.
