Statistics Class 9  – NCERT Solutions for Chapter 12

Statistics Class 9 is a bonus for students that can help them increase their marks to their highest potential. It is an easy-to-understand and straightforward chapter students can take advantage of.

SimplyAcad has provided the NCERT Solutions for Class 9 Maths Chapter 12 Statistics to students for regular practice and revision. The knowledge of statistics is significant in our daily life, and upgrading your statistics skills will surely offer great opportunities in future. Go below to view the solutions of all the exercises of your NCERT textbook.

NCERT Solutions for Class 9 Maths Chapter 12 Statistics Exercise 12.1

Statistics Class 9

Question 1

A survey conducted by an organisation for the cause of illness and death among 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 is 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 are the major cause of women’s ill health and death worldwide.

(iii) Two factors responsible for the cause in (ii) are:

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

Question 2

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

(ii) 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.

Question 3

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

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.

Question 4

 The length of 40 leaves of a plant is measured correct to one millimeter, 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 is 153 mm long? Why?

Solution:

(i) The data given in the question is represented in discontinuous class intervals. So, we have to make it in continuous class intervals. The difference is 1, so taking half of 1, we subtract ½ = 0.5 from the 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 a frequency polygon.

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

Question 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

Question 6

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:
To draw a frequency polygon, we mark the class marks along x-axis. Therefore, the modified table is:

So, the two frequency polygons are as shown below:

From the above frequency polygon, we can see that more students of section A have secured good

Question 7 

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.

Solution:

The given class intervals are not continuous. Therefore, we first modify the distribution as continuous.

Now, the required frequency polygons are as shown below:

 Question 8.

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:

Here, the class sizes are different. So, we calculate the adjusted frequencies corresponding to each rectangle i.e., length of the rectangle.
Adjusted frequency or length of the rectangle

Here, the minimum class size = 2 – 1 = 1
∴ We have the following table for adjusted frequencies or length of rectangles:

Now, the required histogram is shown below:

Question 9.

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) Since, class intervals of the given frequency distribution are unequal, and the minimum class size = 6 – 4 = 2.
Therefore, we have the following table for length of rectangles.

The required histogram is shown below:

(ii) The maximum frequency is 44, which is corresponding to the class interval 6 – 8.
∴ Maximum number of surnames lie in the class interval 6 – 8.