# NCERT Solutions for Class 9 Maths

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# Statistics

Exercise 1

1.     Give some examples of data that you can collect from your day to day life.

2.    Classify the data in Q,1 above as primary or secondary data.

Exercise 2

3.    The blood groups of 30 students of a class VIII are recorded as follows:

A, B, O, O, AB, O, A, O, B, A, O, B, A, O, O, A, AB, O, A, A, O, O, AB, B, A, O, B, A, B, O.

Represent this data in the form of a frequency distribution table. Which is the most common and which is the rarest blood group among these students?

4.   Distance (in km) of 40 engineers from their place of residence to their place of work were found as follows:

5              13        10        20        25        11        13        7          12        31        19        10        12

17            18        11        32        17        16        2          7          9          7          8          3          5

12            15        18        3          12        14        2          9          6          15        15        7          6

12

Construct a grouped frequency distribution table with class size 5 for the data given above taking the first interval as 0 – 5 (5 not included). What main features do you observe from this tabular representation?

5.    The relative humidity (in %) of a certain city for a month of 30 days was as follows:

98.1         98.6                 99.2                 90.3                 86.5                 95.3                     92.9

96.3         94.2                 95.1                 89.2                 92.3                 97.1                     93.5

92.7         95.1                 97.2                 93.3                 95.2                 97.3                     96.2

92.1         84.9                 90.2                 95.7                 98.3                 97.3                     96.1

92.1      89

(i) Construct a grouped frequency distribution table with classes 84 – 86, 86 – 88 etc.

(ii) Which month or season do you think this data is about?

(iii) What is the range of this data?

6.    The heights of 50 students, measured to the nearest centimeters have been found to be as follows:

161         150         154         165         168         161         154         162         150         151         162         164         171

165        158         154         156         172         160         170         153         159         161         170         162         165

166        168         165         164         154         152         153         156         158         162         160         161         173

166        161         159         162         167         168         159         158         153         154         159

(i) Represent the data given above by a grouped frequency distribution table, taking the class – intervals as 160 – 165, 165 – 170 etc.

(ii) What can you conclude about their heights from the table?

7.   A study was conducted to find out the concentration of sulphur dioxide in the air in parts per million (ppm) of a certain city. The data obtained for 30 days is as follows:

0.03        0.08        0.08        0.09        0.04        0.17        0.16        0.05        0.02        0.06        0.18        0.20        0.11

0.08        0.12        0.13        0.22        0.07        0.08        0.01        0.10        0.06        0.09        0.18        0.11        0.07

0.05        0.07        0.01        0.04

(i) Make a grouped frequency distribution table for this data with class intervals as 0.01 – 0.04, 0.04 – 0.08 and so on.

(ii) For how many days, was the concentration of sulphur dioxide more than 0.11 parts per million.

8.   Three coins were tossed 30 times simultaneously. Each time the number of heads occurring was noted down as follows:

0              1              2              2              1              2              3              1              3              0              1              3              1              1

2              2              0              1              2              1              3              0              0              1              1              2              3              2

2              0

Prepare a frequency distribution for the data given above.

9.    The value of π up to 50 decimal places is given below:

3.1415926535       8979323846         2643383279     5028841971     6939937510

(a) Make a frequency distribution of the digits after the decimal point list the digits from 0 to 9 in your first column.

(b) What are the most and the least frequency occurring digits?

10.  Thirty children were asked about the number of hours they watched TV programmes in the previous week. The results were found as follows:

1             6          2          3          5          12        5          8          4          8          10        3          4

12           2          8          15        1          17        6          3          2          8          5          9          6

8          7          14        12

(i) Make a frequency distribution table for this data, taking class width 5 and one of the class interval 5 – 10.

(ii) How many children watched television for 15 or more hours a week?

11.  A company manufactures car-batteries of particular type. The live (in years) of 40 such batteries were recorded as follows:

2.6          3.0       3.7       3.2       2.2       4.1       3.5       4.5       3.5       2.3       3.2       3.4       3.8

3.2          4.6       3.7       2.5       4.4       3.4       3.3       2.9       3.0       4.3       2.8       3.5       3.2

3.9          3.2       3.2       3.1       3.7       3.4       4.6       3.8       3.2       2.6       3.5       4.2       2.9

3.6

Construct a grouped frequency distribution table for this data, using class intervals of size 0.5 starting from the interval 2 – 2.5.

Exercise 3

12.  A survey conducted by an organization for the cause of illness and death among the women between the ages 15 – 44 (in years) worldwide, found the following figures (in %):

(i) Represent the information given above graphically.

(ii) Which condition is the major cause of women’s ill health and death worldwide?

(iii) Try to find out, with the help of your teacher, any two factors which play a major role in the cause in (ii) above being the major cause.

13.  The following data on the number of girls (to the nearest ten) per thousand boys in different sections of Indian Society is given below:

(i) Represent the information above by a bar graph.

(ii) In the classroom discuss what conclusions can be arrived at from the graph.

14.  Given below are the seats won by different political parties in the polling outcome of a state assembly elections:

(i) Draw a bar graph to represent the polling results

(ii) Which political party won the maximum number of seats?

15.  The length of 40 leaves of a plant are measured correct to one millimeter and the obtained data is represented in the following table:

(i) Draw a histogram to represent the given data.

(ii) Is there any other suitable graphical representation for the same data?

(iii) Is it correct to conclude that the maximum number of leaves are 153 mm long? Why?

16.  The following table gives the life times of 400 neon lamps:

(i) Represent the given information with the help of a histogram.

(ii) How many lamps have a life time of more than 700 hours?

17.  The following table gives the distribution of students of two sections according to the marks obtained by him:

Represent the marks of the students of both the sections on the same graph by two frequency polygons. From the two polygons compare the performance of the two sections.

18.  The runs scored by the two teams A and B in the first 60 balls in a cricket match are given below:

Represent the data of both the teams on the same graph by frequency polygons.

19.  A random survey of the number of children of various age groups playing in a park was found as follows:

Draw a histogram to represent the data above.

20.  100 surnames were randomly picked up from a local telephone directory and a frequency distribution of the number of letters in the English alphabet in the surnames was found as follows:

(i) Draw a histogram to depict the given information.

(ii) Write the class interval in which the maximum number of surnames lie.

Exercise 4

21.  The following number of goals were scored by a team in a series of 10 matches:

2, 3, 4, 5, 0, 1, 3, 3, 4, 3

Find the mean, median and mode of these scores.

22.  In a mathematics test given to 15 students, the following marks (out of 100) are recorded:

41, 39, 48, 52, 46, 62, 54, 40, 96, 52, 98, 40, 42, 52, 60

Find the mean, median and mode of this data.

23.  The following observations have been arranged in the ascending order. If the median of the data is 63, find the value of x :

29, 32, 48, 52, x, x + 2, 72, 78, 84, 95

24.  Find the mode of the following data in each case:

(i) 14, 25, 14, 28, 18, 17, 18, 14, 23, 22, 14, 18

(ii) 7, 9, 12, 13, 7, 12, 15, 7, 12, 7, 25, 18, 7

25.  Find the mean salary of 60 workers of a factory from the following table:

26.  Give an example of a situation in which:

(i) The mean is an appropriate measure of central tendency.

(ii) The mean is not an appropriate measure of central tendency but the median is an appropriate measure of central tendency.

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