Advertisements
Advertisements
Question
There are 45 students in a class, in which 15 are girls. The average weight of 15 girls is 45 kg and 30 boys is 52 kg. Find the mean weight in kg of the entire class.
Solution
Here n1 = 15, n2 = 30, X1 = 45 Kg and X2 = 52 Kg.
∴ `bar"X"` = `("n"_1bar"X"_1 + "n"_2bar"X"_2)/("n"_1 + "n"_2) = (15 xx 45 + 30 xx 52)/(15 + 30)"Kg"`.
= `(2235)/(45)"kg"`
= 49·67kg.
Hence, the mean weight of the entire class is 49·67kg.
APPEARS IN
RELATED QUESTIONS
If the mean of the following data is 15, find p.
| x | 5 | 10 | 15 | 20 | 25 |
| f | 6 | P | 6 | 10 | 5 |
The marks obtained out of 50, by 102 students in a Physics test are given in the frequency table below:
| Marks(x) | 15 | 20 | 22 | 24 | 25 | 30 | 33 | 38 | 45 |
| Frequency (f) | 5 | 8 | 11 | 20 | 23 | 18 | 13 | 3 | 1 |
Find the average number of marks.
Find the mean of each of the following frequency distributions
| Class interval | 0 - 8 | 8 - 16 | 16 - 24 | 24 - 32 | 32 - 40 |
| Frequency | 5 | 6 | 4 | 3 | 2 |
Find the mean of each of the following frequency distributions
| Class interval | 10 - 30 | 30 - 50 | 50 - 70 | 70 - 90 | 90 - 110 | 110 - 130 |
| Frequency | 5 | 8 | 12 | 20 | 3 | 2 |
The daily expenditure of 100 families are given below. Calculate `f_1` and `f_2` if the mean daily expenditure is ₹ 188.
|
Expenditure (in Rs) |
140-160 | 160-180 | 180-200 | 200-220 | 220-240 |
|
Number of families |
5 | 25 | `f_1` | `f_2` | 5 |
Weight of 60 eggs were recorded as given below:
| Weight (in grams) | 75 – 79 | 80 – 84 | 85 – 89 | 90 – 94 | 95 – 99 | 100 - 104 | 105 - 109 |
| No. of eggs | 4 | 9 | 13 | 17 | 12 | 3 | 2 |
Calculate their mean weight to the nearest gram.
If Σfi = 25 and Σfixi = 100, then find the mean (`bar"x"`)
The mean weight of 150 students in a certain class is 60 kgs. The mean weight of boys in the class is 70 kg and that of girls is 55 kgs. Find the number of boys and the number of girls in the class.
Mean of 100 items is 49. It was discovered that three items which should have been 60, 70, 80 were wrongly read as 40, 20, 50 respectively. The correct mean is ______.
(For an arranged data) The median is the ______.
