Q24 of 37 Page 14

The following table gives the literacy rate (in percentage) in 40 cities. Find the mean literacy rate, choosing a suitable method. [CBSE 2014]


Literacy rate (%)

45 - 55

55 - 65

65 - 75

75 - 85

85 - 95

Number of cities

4

11

12

9

4

We will solve this using direct method.


LITERACY RATE(%)

MID - POINT(xi)

NUMBER OF CITIES(fi)

fixi

45 - 55

50

4

200

55 - 65

60

11

660

65 - 75

70

12

840

75 - 85

80

9

720

85 - 95

90

4

360

TOTAL

  

40

2780

We have got


Σfi = 40 and Σfixi = 2780


∵ mean is given by



⇒


⇒


Thus, mean is 69.5%.

More from this chapter

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22

Heights of students of Class X are given in the following frequency distribution: [CBSE 2014]


Height (in cm)

150 - 155

155 - 160

160 - 165

165 - 170

170 - 175

Number of students

15

8

20

12

5

Find the modal height.


Also, find the mean height. Compare and interpret the two measures of central tendency.

 23

In an annual examination, marks (out of 90) obtained by students of Class X in mathematics are given below: [CBSE 2014]


Marks obtained

0 - 15

15 - 30

30 - 45

45 - 60

60 - 75

75 - 90

Number of students

2

4

5

20

9

10

Find the mean marks.

 25

Find the mean of the following frequency distribution using step - deviation method. [CBSE 2014]


Class

0 - 10

10 - 20

20 - 30

30 - 40

40 - 50

Frequency

7

10

15

8

10
26

The mean of the following data is 42. Find the missing frequencies x and y if the Sum of frequencies is 100.[CBSE 2014]


Class interval

0 - 10

10 - 20

20 - 30

30 - 40

40 - 50

50 - 60

60 - 70

70 - 80

Frequency

7

10

x

13

y

10

14

9