The distribution below gives the weights of 30 students of a class. Find the median weight of the students.
| Weight (in kg) | 40 - 45 | 45 - 50 | 50 - 55 | 65 - 60 | 70- 65 | 65 - 70 | 70 - 75 |
|---|---|---|---|---|---|---|---|
| Number of students | 2 | 3 | 8 | 6 | 6 | 3 | 2 |
100 surnames were randomly picked up from a local telephone directory and the frequency distribution of the number of letters in the English alphabets in the surnames was obtained as follows:
Number of letters | 1 - 4 | 4 - 7 | 7 - 10 | 10 - 13 | 13 - 16 | 16 - 19 |
|---|---|---|---|---|---|---|
Number of surnames | 6 | 30 | 40 | 16 | 4 | 4 |
Determine the median number of letters in the surnames. Find the mean number of letters in the surnames? Also, find the modal size of the surnames.
The following table gives the distribution of the life time of 400 neon lamps :
| Life time (in hours) | Number of lamps |
|---|---|
1500 - 2000 | 14 |
2000 - 2500 | 56 |
2500 - 3000 | 60 |
3000 - 3500 | 86 |
3500 - 4000 | 74 |
4000 - 4500 | 62 |
4500 - 5000 | 48 |
Find the median life time of a lamp.
The lengths of 40 leaves of a plant are measured correct to the nearest millimetre, and the data obtained is represented in the following table :
Length (in mm) | Number of leaves |
|---|---|
118 - 126 | 3 |
127 - 135 | 5 |
136 - 144 | 9 |
145 - 153 | 12 |
154 - 162 | 5 |
163 - 171 | 4 |
172 - 180 | 2 |
Find the median length of the leaves.
(Hint : The data needs to be converted to continuous classes for finding the median, since the formula assumes continuous classes. The classes then change to 117.5 - 126.5, 126.5 - 135.5, . . ., 171.5 - 180.5.)
A life insurance agent found the following data for distribution of ages of 100 policy holders. Calculate the median age, if policies are given only to persons having age 18 years onwards but less than 60 year.
Age (in years) | Number of policy holders |
|---|---|
Below 20 | 2 |
Below 25 | 6 |
Below 30 | 24 |
Below 35 | 45 |
Below 40 | 78 |
Below 45 | 89 |
Below 50 | 92 |
Below 55 | 98 |
Below 60 | 100 |
| Case No. | Lens | Focal Length | Object Distance |
|---|---|---|---|
| 1 | \(A\) | 50 cm | 25 cm |
| 2 | B | 20 cm | 60 cm |
| 3 | C | 15 cm | 30 cm |