Page 320 - Start Up Mathematics_8 (Non CCE)

Solution: Frequency Distribution of Marks of 20 Students

Marks Tally marks Frequency
15 | | 2
16 | | | 3
18 | | 2
20 | 6
22 5
23 | | 2
Total 20

EXERCISE 20.1
1. A survey was conducted in 25 families of a locality. Given below are the number of children in these
families. Prepare a frequency distribution of the data.
2, 2, 3, 1, 1, 1, 2, 2, 3, 2, 2, 2, 1, 1, 1, 1, 2, 2, 3, 1, 2, 2, 1, 2, 2
2. Following are the marks of 35 students in an examination:
20, 16, 19, 25, 30, 20, 20, 19, 25, 25, 16, 30, 30, 28, 12, 5, 21, 23, 28, 24, 10, 8, 17, 22, 20, 23, 29,
15, 10, 10, 14, 25, 21, 11, 2
(a) Arrange the following data in ascending order.
(b) What are the highest marks?
(c) What are the lowest marks?
(d) Find the range of the above data.
(e) If 12 are the passing marks, how many students failed in the class?
(f) How many students scored above 25 marks?
3. The ages of 25 patients who visited a dentist are given below. Prepare a frequency distribution of
the data.
34, 35, 39, 38, 4, 9, 15, 26, 12, 13, 25, 32, 3, 12, 39, 14, 12, 12, 24, 8, 21, 16, 5, 12, 30
(a) What is the age of the youngest patient?
(b) What is the age of patients who visited the dentist maximum number of times?
(c) How many patients are above 30 years of age?
4. Given below are the heights of 15 students (in cm) of class VIII of a school. Prepare a discrete
frequency distribution.
128, 130, 125, 148, 142, 130, 130, 125, 128, 130, 148, 125, 142, 130, 130

5. A die was thrown 20 times and given below are the scores. Prepare a discrete frequency
distribution.
2, 3, 1, 2, 4, 6, 5, 2, 3, 1, 4, 3, 6, 6, 1, 1, 2, 4, 5, 2
6. The rainfall (in mm) in a city on 7 days of a certain week was recorded as follows:

Day Mon Tue Wed Thu Fri Sat Sun
Rainfall (in mm) 2.2 21.3 25.6 0.0 4.9 0.0 5.5

(a) Find the range of rainfall in the above data.
(b) On how many days was there no rainfall?

Construction of a Grouped Frequency Distribution
Step 1: Find the maximum and minimum values of the variates occurring in the data.
Step 2: Decide upon the number of classes to be formed, preferably from 5 to 15 classes.

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