 # NCERT Solutions for Class 9 Maths Chapter 14- Statistics

NCERT Solutions for Class 9 Maths Chapter 14 Statistics is one of the best ways to strengthen one’s skills and knowledge. It contains all the relevant study material that can help the students score well in the examinations. NCERT Solutions Class 9 Chapter 14- Statistics is an important chapter from the examination perspective. A proper understanding of this chapter will help the students with a few chapters in the higher classes as well.

Solutions to the questions given in the textbook are provided in the NCERT Solutions for Class 9. The solutions are provided by the subject experts and are accurate. Every question is explained stepwise for a better understanding of the students. The students can refer to these for reference purposes. NCERT Solutions is the best guide for the students. The students should go through the solutions after completing every chapter. This will help them analyse their weaknesses and improve on them.

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#### Class 9 Maths Chapter 14 Exercise 14.1 Page: 239

Q1. Give five examples of data that you can collect from your day-to-day life.

Solution:

Five examples from day-to-day life:

i Number of students in our class.

• Number of fans in our school.
• Electricity bills of our house for last two years.
• Election results obtained from television or newspapers.
• Literacy rate figures obtained from Educational Survey

Q2. Classify the data in Q.1 above as primary or secondary data.

Solution:

Primary data: when the information was collected by the investigator herself or himself with a definite objective in her or his mind, the data obtained is called primary data.

Primary data; (i), (ii) and (iii)

Secondary data; when the information was gathered from a source which already had the information stored, the data obtained is called secondary data

Secondary data; (iv) and (v)

#### Exercise 14.2 Page: 245

Q1. The blood groups of 30 students of 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?

Solution:

Frequency is the number of students having the same blood group. The frequency is represented in the table or the frequency distribution table:

 Blood Group Number of Students (Frequency) A 9 B 6 O 12 AB 3 Total 30

The most common Blood Group is the blood group with highest frequency: O

The rarest Blood Group is the blood group with lowest frequency: AB

Q2. The distance (in km) of 40 engineers from their residence to their place of work were found as follows:
5    3    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?

Solution:

Since the given data is very large, we construct a grouped frequency distribution table of class size 5. , class interval will be 0-5, 5-10, 10-15, 15-20 and so on. The data is represented in the grouped frequency distribution table as: In the given table the classes do not overlap. Also we find that, the houses of 36 out of 40 engineers are below 20 km of distance

Q3. 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?

Solution:

(i)Since the given data is very large, we construct a grouped frequency distribution table of class size 2. , class interval will be 84-86, 86-88, 88-90, 90-92 and so on. The data is represented in the grouped frequency distribution table as:

 Relative humidity (in %) Frequency 84-86 1 86-88 1 88-90 2 90-92 2 92-94 7 94-96 6 96-98 7 98-100 4 Total 30

(ii) The humidity is very high in the given data. Since the humidity is observed to be high during the rainy season, the data here must be about rainy season.
(iii)The range of a data
= The maximum value of the data – minimum value of the data
= 99.2 − 84.9
= 14.3

Q4. 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?

Solution:

(i) The data given in the question can be represented by a grouped frequency distribution table, taking the class intervals as 160 – 165, 165 – 170, etc., as:

 Height (in cm) No. of Students (Frequency) 150-155 12 155-160 9 160-165 14 165-170 10 170-175 5 Total 50

(ii) It can be concluded from the given data and the table that 35 students, i.e. more than 50% of the total students, are shorter than 165 cm.

5. 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 0.00 – 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?

Solution:

(i)The grouped frequency distribution table for the data given in the question with class intervals as 0.00 – 0.04, 0.04 – 0.08, and so on is given below.

 Concentration of sulphur dioxide in air (in ppm) Frequency 0.00 − 0.04 4 0.04 − 0.08 9 0.08 − 0.12 9 0.12 − 0.16 2 0.16 − 0.20 4 0.20 − 0.24 2 Total 30

(ii) The number of days in which the concentration of sulphur dioxide was more than 0.11 parts per million = 2 + 4 + 2 = 8

Q6. 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 table for the data given above.

Solution:

The frequency distribution table for the data given in the question is given below:

 Number of Heads Frequency 0 6 1 10 2 9 3 5 Total 30

Q7. The value of π upto 50 decimal places is given below:

3.14159265358979323846264338327950288419716939937510

(i) Make a frequency distribution of the digits from 0 to 9 after the decimal point.
(ii)What are the most and the least frequently occurring digits?

Solution:

(i) The frequency distribution of the digits from 0 to 9 after the decimal point is given in the table below:

 Digits Frequency 0 2 1 5 2 5 3 8 4 4 5 5 6 4 7 4 8 5 9 8 Total 50

(ii) The digit having the least frequency occurs the least. Since 0 occurs only twice, it has a frequency of 2. The least frequently occurring digit is 0.

The digit with highest frequency occurs the most. Since 3 and 9 occurs eight times, it has a frequency of 8. The most frequently occurring digits are 3 and 9.

Q8. 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 grouped frequency distribution table for this data, taking class width 5 and one of the class intervals as 5-10.
(ii) How many children watched television for 15 or more hours a week?

Solution:

i) The grouped frequency distribution table for the data given in the question, taking class width 5 and one of the class intervals as 5-10 is given below:

 Number of Hours Frequency 0-5 10 5-10 13 10-15 5 15-20 2 Total 30

ii) From the given table, we can conclude that 2 children watched television for 15 or more hours in a week.

9. A company manufactures car batteries of a particular type. The lives (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.

Solution:

The grouped frequency distribution table for the data given in the table, using class intervals of size 0.5 starting from the interval 2 – 2.5, is given below.

 Lives of batteries (in years) No. of batteries (Frequency) 2-2.5 2 2.5-3 6 3-3.5 14 3.5-4 11 4-4.5 4 4.5-5 3 Total 40

#### Exercise 14.3 Page: 258

Q1. A survey conducted by an organisation for the cause of illness and death among the women between the ages 15 – 44 (in years) worldwide, found the following figures (in %):

 S.No. Causes Female fatality rate (%) 1. Reproductive health conditions 31.8 2. Neuropsychiatric conditions 25.4 3. Injuries 12.4 4. Cardiovascular conditions 4.3 5. Respiratory conditions 4.1 6. Other causes 22.0

(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.

Solution:

i) The information given in the question is represented below graphically. (ii) We can observe from the graph that reproductive health conditions is the major cause of women’s ill health and death worldwide.
(iii) Two factors responsible for cause in (ii) are:

• Lack of proper care and understanding.
• Lack of medical facilities.

Q2. The following data on the number of girls (to the nearest ten) per thousand boys in different sections of Indian society is given below.

 S.No. Section Number of girls per thousand boys 1. Scheduled Caste (SC) 940 2. Scheduled Tribe (ST) 970 3. Non SC/ST 920 4. Backward districts 950 5. Non-backward districts 920 6. Rural 930 7. Urban 910

(i) Represent the information above by a bar graph.
(ii) In the classroom discuss what conclusions can be arrived at from the graph.

Solution:

(i) The information given in the question is represented below graphically. (i) From the above graph, we can conclude that the maximum number of girls per thousand boys is present in the section ST. We can also observe that the backward districts and rural areas have more number of girls per thousand boys than non-backward districts and urban areas.

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

 Political party A B C D E F Seats won 75 55 37 29 10 37

(i) Draw a bar graph to represent the polling results.
(ii) Which political party won the maximum number of seats?

Solution:

(i) The bar graph representing the polling results is given below: (ii) From the bar graph it is clear that Party A won the maximum number of seats.

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

 S.No. Length (in mm) Number of leaves 1. 118 – 126 3 2. 127 – 135 5 3. 136 – 144 9 4. 145 – 153 12 5. 154 – 162 5 6. 163 – 171 4 7. 172 – 180 2

(i) Draw a histogram to represent the given data. [Hint: First make the class intervals continuous]
(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?

Solution:

(i) The data given in the question is represented in discontinuous class interval. So, we have to make it in continuous class interval. The difference is 1, so taking half of 1, we subtract = 0.5 from lower limit and add 0.5 to the upper limit. Then the table becomes:

 S.No. Length (in mm) Number of leaves 1. 117.5 – 126.5 3 2. 126.5 – 135.5 5 3. 135.5 – 144.5 9 4. 144.5 – 153.5 12 5. 153.5 – 162.5 5 6. 162.5 – 171.5 4 7. 171.5 – 180.5 2 (ii) Yes, the data given in the question can also be represented by frequency polygon.

(iii) No, we cannot conclude that the maximum number of leaves are 153 mm long because the maximum number of leaves are lying in-between the length of 144.5 – 153.5

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

 Life Time (in hours) Number of lamps 300 – 400 14 400 – 500 56 500 – 600 60 600 – 700 86 700 – 800 74 800 – 900 62 900 – 1000 48

(i) Represent the given information with the help of a histogram.
(ii) How many lamps have a life time of more than 700 hours?

Solution:

(i) The histogram representation of the given data is given below: (ii)

The number of lamps having a life time of more than

700 hours = 74 + 62 + 48

= 184

Q6. The following table gives the distribution of students of two sections according to the marks obtained by them: 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.

Solution:

The class-marks = (Lowest limit + Upper limit)/2

For section A,

 Marks Class-marks Frequency 0-10 5 3 10-20 15 9 20-30 25 17 30-40 35 12 40-50 45 9

For section B,

 Marks Class-marks Frequency 0-10 5 5 10-20 15 19 20-30 25 15 30-40 35 10 40-50 45 1

Representing these data on a graph using two frequency polygon we get, From the graph, we can conclude that the students of Section A performed better than Section B.

Q7. The runs scored by two teams A and B on 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.

[Hint: First make the class intervals continuous.]

Solution:

The data given in the question is represented in discontinuous class interval. So, we have to make it in continuous class interval. The difference is 1, so taking half of 1, we subtract = 0.5 from lower limit and add 0.5 to the upper limit. Then the table becomes:

 Number of balls Team A Team B 0.5-6.5 2 5 6.5-12.5 1 6 12.5-18.5 8 2 18.5-24.5 9 10 24.5-30.5 4 5 30.5-36.5 5 6 36.5-42.5 6 3 42.5-48.5 10 4 48.5-54.5 6 8 54.5-60.5 2 10

The data of both the teams are represented on the graph below by frequency polygons. Q8. 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.

Solution:

The width of the class intervals in the given data is varying.

We know that,

the area of rectangle is proportional to the frequencies in the histogram.

Thus, the proportion of the children per year can be calculated as given in the table below.

 Age (in years) Number of children (frequency) Width of class Length of rectangle 1-2 5 1 (5/1)×1 = 5 2-3 3 1 (3/1)×1 = 3 3-5 6 2 (6/2)×1 = 3 5-7 12 2 (12/2)×1 = 6 7-10 9 3 (9/3)×1 = 3 10-15 10 5 (10/5)×1 = 2 15-17 4 2 (4/2)×1 = 2

Let x-axis = the age of children

y-axis = proportion of children per 1 year interval Q9. 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.

Solution:

(i) The width of the class intervals in the given data is varying.

We know that,

the area of rectangle is proportional to the frequencies in the histogram.

Thus, the proportion of the number of surnames per 2 letters interval can be calculated as given in the table below.

 Number of letters Number of surnames Width of class Length of rectangle 1-4 6 3 (6/3)×2 = 4 4-6 30 2 (30/2)×2 = 30 6-8 44 2 (44/2)×2 = 44 8-12 16 4 (16/4)×2 = 8 12-20 4 8 (4/8)×2 = 1 (ii) 6-8 is the class interval in which the maximum number of surnames lie.

#### Exercise 14.4 Page: 269

Q1. 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.

Solution: = $\frac{3+3}{2}$
= 3

Mode,

To find the mode, we first arrange the data in ascending order.

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

Here,

We find that 3 occurs most frequently (4 times)

∴ Mode = 3

Q2. 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. Q3. The following observations have been arranged in ascending order. If the median of the data is 63, find the value of x.

29, 32, 48, 50, x, x+2, 72, 78, 84, 95

Solution:

Number of observations (n) = 10

Given that Median = 63

Since the number of observations are even, the median can be calculated as: Q4. Find the mode of 14, 25, 14, 28, 18, 17, 18, 14, 23, 22, 14, 18.

Solution:

Mode,

To find the mode, we first arrange the given data in ascending order.

14,14,14,14,17,18,18,18,22,23,25,28

Here,

We find that 14 occurs most frequently (4 times)

∴ Mode = 14

Q5.  Find the mean salary of 60 workers of a factory from the following table: Solution:

 Salary (xi) Number of workers (fi) fixi 3000 16 48000 4000 12 48000 5000 10 50000 6000 8 48000 7000 6 42000 8000 4 32000 9000 3 27000 10000 1 10000 Total Σfi = 60 Σfixi = 305000 , the mean salary is ₹5083.33

Q6. Give one 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.

Solution:

(i) ## NCERT Solutions for Class 9 Chapter 14- Statistics

Chapter 14- Statistics of NCERT Solutions Class 9 carries a weightage of 10 marks in the examination. It is an important chapter, therefore, one needs to be thorough with the concepts. The accurate, stepwise solutions are provided in the NCERT Solutions Class 9 Chapter 14 Statistics.

List of Exercises in class 9 Maths Chapter 14 :

Exercise 14.1 Solutions 2 Questions

Exercise 14.2 Solutions 9 Questions

Exercise 14.3 Solutions 9 Questions

Exercise 14.4 Solutions 6 Questions

 Also Access NCERT Exemplar for class 9 Maths Chapter 14 CBSE Notes for class 9 Maths Chapter 14

## NCERT Solutions for Class 9 Chapter 14- Statistics

Statistics is the branch of statistics dealing with the collection, organization, interpretation, analysis, and presentation of data. If statistics is applied to a scientific, industrial, or social problem, one should begin with with a statistical model or a statistical population to be studied.

Statistical methods are mathematical models, formulas, and techniques that are used in the statistical research of raw research data.

### Key Features of NCERT Solutions for class 9 Maths Chapter 14- Statistics

• The solutions are provided by the subject experts.
• NCERT Solutions for Class 9 Maths Chapter 14- Statistics will help the students score well in the examinations.
• The answers to the questions provided are accurate.
• All the questions mentioned in the textbook can be found along with the solutions in the NCERT Solutions Maths Class 9.