Important Questions & Solutions of Class 9 Maths Chapter 14 – Statistics

ncert for class 9th maths

Question 1. Give three examples of data which you can get from your day-to-day life.

Solution:

Here are the three examples which are related to our day-to-day life :

• The number of boys in a sports team.
• Electricity bills for last one year.
• The number of students appearing for board exams at your school.

Question 2. The height of 20 students of class V are noted as follows

4, 4.5, 5, 5.5, 4, 4, 4.5, 5, 5.5, 4, 3.5, 3.5, 4.2, 4.6, 4.2, 4.7, 5.5, 5.3, 5, 5.5.

1. Make a frequency distribution table for the above data.
2. Which is the most common height and which is the rarest height among these students?

Solution:

1. The required frequency distribution table is:

2. The most common heights are 4 and 5.5.
The rarest heights are 4.6 and 4.7.

Question 3: The number of family members in 10 flats of society are

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

Find the mean number of family members per flat.

Solution:

Number of family members in 10 flats -2, 4, 3, 3, 1, 0, 2, 4, 1, 5.

So, we get,

Mean = sum of observation/ total no of observations

Mean = (2 + 4+ 3 + 3 + 1 + 0 + 2 + 4 + 1 + 5) / 10

Mean = 25/10 = 2.5

Question 4.The following is the list of number of coupons issued in a school canteen during a week:

105, 216, 322, 167, 273, 405 and 346.

Find the average no. of coupons issued per day.

Solution:

Number of coupons issued in a week: 105, 216, 322, 167, 273, 405 and 346.

So, we get,

Mean = sum of observation/ total no of observations

Mean = 106+ 215+ 323+166+273+405+346/ 7 = 1834/7

Mean = 262

Question 5. The daily minimum questions solved by a student during a week were as under:

Find the mean.

Solution: 

Number of questions solved in a week: 35, 30, 27, 32, 23, 28.

So, we get,

Mean = sum of observation/ total no of observations = (35+30+27+32+23+28) / 7 = 175/7 = 25

Question 6.If the mean of six observations y, y + 1, y + 4, y + 6, y + 8, y + 5 is 13, find the value of y.

Solution:

Mean = sum of observation/ total no of observations

13 = (y + y + 1+ y + 4+ y + 6+ y + 8+ y + 5) / 6

13 = (6y + 24)/6

(13 * 6) = 6y +24

(13 * 6) – 24 = 6y

(13 * 6) – 6 * 4 = 6y

6(13 – 4) = 6y

y = 9

Question 7. The mean weight of a class of 34 students is 46.5 kg. If the weight of the new boy is included, the mean is rises by 500 g. Find the weight of the new boy.

Solution:

The mean weight of 34 students = 46.5

Sum of the weight of 34 students = (46.5 * 34) = 1581

Change or increase in the mean weight when the weight of a new boy is added = 0.5

So, the new mean = (46.5 +0.5) = 47

So, let the weight of the new boy be y.

So, (sum of weight of 34 students + weight of new boy) / 35 = 47

(1581+ y)/ 35 = 47

1581 + y = 1645

y = 1645 – 1581 = 64

Question 8.The Number of books issued to 13 students in a class are:

25, 19, 24, 23, 29, 31, 19, 20, 22, 26, 17, 35, 21.

Find the median no. of books for the above data.

Solution:

Let’s arrange the data given in ascending order – 17, 19, 19, 20, 21, 22, 23, 24, 25, 26, 29,31,35.

n= 13, so it’s an odd number

Median = (n+1) / 2 observations

= (13+1)/ 2 = (14/2)^th observation = 7th observation = 23

Question 9.The weight (in kg) of 7 students of a class are 44, 52, 55, 60, 50, 49, 45.

Find the median weight.

Solution:

Let’s arrange the data given in ascending order – 44, 45, 49, 50, 52, 55, 60.

n= 7, so it’s an odd number

Median = (n+1) / 2 observations

= (7+1)/ 2 = (8/2)^th observation = 4th observation = 50 kg

Extra Questions For Class 9 Maths Chapter 14 (Statistics)

1. Find the mean and median of the following data: 25, 26, 27, 28, 28, 29, 25, 30, 29
2. 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?
3. The value of π up to 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?