Advertisements
Advertisements
Question
The mean of three numbers is 10. The mean of other four numbers is 12. Find the mean of all the numbers.
Solution
Mean of three numbers = `"Sum of three numbers"/3`
⇒ 10 = `"Sum of three numbers"/3` ......[∵ Mean of three numbers = 10, given]
Here, sum of three numbers = 30
Mean of other four numbers = `"Sum of other four numbers"/4`
⇒ 12 = `"Sum of other four numbers"/4` .....`[(∵ "Mean of other four"),("numbers" = 12"," "given")]`
Hence, sum of other four numbers = 48
∴ Mean of all the numbers = `"Sum of all the numbers"/"Total numbers"`
= `(["Sum of first three numbers" + "Sum of other four numbers"])/7`
= `(30 + 48)/7`
= `78/7`
= 11.14
Hence, mean of all the numbers is 11.14.
APPEARS IN
RELATED QUESTIONS
If `barx` is the mean of x1, x2 ............xn and `bary` is the mean of y1, y2, …….yn and `barz` is the mean of x1, x2 ............xn, y1, y2, ……….yn then `barz` =?
The following table shows the number of saplings planted by 30 students. Fill in the boxes and find the average number of saplings planted by each student.
| No. of saplings (Scores) xi |
No. of students (frequency) fi |
fi x xi |
| 1 | 4 | 4 |
| 2 | 6 | `square` |
| 3 | 12 | `square` |
| 4 | 8 | `square` |
| N = `square` | ∑fixi = `square` |
Mean `bar "x"` = `square/"N"`
= `square/square`
= `square`
∴ The average number of trees planted `square`
The number of Science and Mathematics projects submitted by Model high school, Nandpur in last 20 years at the state level science exibition is:
2, 3, 4, 1, 2, 3, 1, 5, 4, 2, 3, 1, 3, 5, 4, 3, 2, 2, 3, 2. Prepare a frequency table and find the mean of the data.
The following table shows the electricity (in units) used by 25 families of Eklara village in a month of May. Complete the table and answer the following questions.
| Electricity used (units) `bb(x_i)` |
No. of Families (frequency) `bb(f_i)` |
`bb(f_ix_i)` |
| 30 | 7 | _________ |
| 45 | 2 | __________ |
| 60 | 8 | __________ |
| 75 | 5 | __________ |
| 90 | 3 | __________ |
| N = _________ | `sum f_ix_i` = ______ |
- How many families use 45 units electricity?
- State the score, the frequency of which is 5.
- Find N, and `sum f_ix_i`
- Find the mean of electricity used by each family in the month of May.
The mean weight of 4 members of a family is 60 kg. Three of them have the weight 56 kg, 68 kg and 72 kg respectively. Find the weight of the fourth member
The mean of a set of seven numbers is 81. If one of the numbers is discarded, the mean of the remaining numbers is 78. The value of discarded number is
Which measures of central tendency get affected if the extreme observations on both the ends of a data arranged in descending order are removed?
The mean of a data is defined as ______.
Mean of the data is always from the given data.
The mean age of 25 teachers in a school is 40 years. A teacher retires at the age of 60 years and a new teacher is appointed in his place. If the mean age of the teachers in this school now is 39 years, then the age (in years) of the newly appointed teacher is ______.
