Page 194 - Maths Skills - 8

192 Maths

Groups Tally marks Frequency

12–19 || 2 (a) Number of students who have scored less
than 40 = 2 + 2 + 3 + 6 = 13
19–26 || 2
(b) Class mark of the interval 54–61 with
26–33 ||| 3 (54 + 61)
frequency 10 is = = 57.5
33–40 |||| | 6 2

(c) The class interval 47–54 has the highest
40–47 |||| | 6 frequency of 11.

47–54 |||| |||| | 11 (d) Number of students who scored more than

61 = 6 + 2 + 2 = 10
54–61 |||| |||| 10 Total number of students = 50
Hence, percentage of students who scored
61–68 |||| | 6 10

68–75 || 2 more than 61 is 50 × 100% = 20%.

75–82 || 2

Total = 50

Exercise 12.1

1. A class of 30 students took a mock exam in mathematics. They were given percentage of marks
as follows:

62, 20, 48, 50, 78, 91, 57, 82, 46, 51, 62, 50, 72, 73, 63, 52, 41, 37, 28, 46, 71, 75, 36, 28, 44, 90, 51, 28, 60, 18.
Construct a frequency distribution table using equal class intervals.

2. A factory has a census of its workers. There are 50 workers in total. The data given below shows
their ages:
34, 28, 22, 36, 27, 18, 52, 39, 42, 29, 35, 31, 27, 22, 37, 34, 19, 20, 57, 49, 50, 37, 46, 25, 17, 37, 42, 53, 41,
51, 35, 24, 33, 41, 53, 60, 18, 44, 38, 41, 48, 27, 39, 19, 30, 61, 54, 48, 26, 18.
(i) Make a table grouping the data into classes from 10 to 19, 20 to 29, 30 to 39, 40 to 49 and so on.

(ii) Make a table grouping the data into classes from 15 to 19, 19 to 23, 23 to 27, 27 to 31, 31 to 35 and so on.
3. Rishi did a survey of how many games each of his 20 friends owned and collected the data as:

9, 15, 11, 12, 3, 5, 10, 20, 14, 6, 8, 8, 12, 12, 18, 15, 6, 9, 18, 11
Prepare a frequency distribution table with class intervals of 5 games and then answer the following questions:
(i) What was the total number of games his friends owned?

(ii) Which class interval has the least frequency?
(iii) What is the class mark of the third class interval?