Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling

Selina Publishers Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling

Data Handling Exercise 21A – Selina Concise Mathematics Class 7 ICSE Solutions

Question 1.
Consider the following numbers :
68, 76, 63, 75, 93, 83, 70, 115, 82, 105, 90, 103, 92, 52, 99, 73, 75, 63, 77 and 71.
(i) Arrange these numbers in ascending order.
(ii) What the range of these numbers?
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21A 1

Question 2.
Represent the following data in the form of a frequency distribution table :
16, 17, 21, 20, 16, 20, 16, 18, 17, 21, 17, 18, 19, 17, 15, 15, 19, 19, 18, 17, 17, 15, 15, 16, 17, 17, 19, 18, 17, 16, 15, 20, 16, 17, 19, 18, 19, 16, 21 and 17.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21A 2

Question 3.
A die was thrown 20 times and following scores were recorded.
2, 1, 5, 2, 4, 3, 6, 1, 4, 2, 5, 1, 6, 2, 6, 3, 5, 4, 1 and 3.
Prepare a frequency table for the scores.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21A 3

Question 4.
Following data shows the weekly wages (in ₹) of 10 workers in a factory.
3500, 4250, 4000, 4250, 4000, 3750, 4750, 4000, 4250 and 4000
(i) Prepare a frequency distribution table.
(ii) What is the range of wages (in ₹)?
(iii) How many workers are getting the maximum wages?
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21A 4

Question 5.
The marks obtained by 40 students of a class are given below :
80, 10, 30, 70, 60, 50, 50, 40, 40, 20, 40, 90, 50, 30, 70, 10, 60, 50, 20, 70, 70, 30, 80, 40,20, 80, 90, 50, 80, 60, 70, 40, 50, 60, 90, 60, 40, 40, 60 and 60
(i) Construct a frequency distribution table.
(ii) Find how many students have marks equal to or more than 70?
(iii) How many students obtained marks below 40?
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21A 5

Question 6.
Arrange the following data in descending order:
3.3, 3.2, 3.1, 3.7, 3.6, 4.0, 3.5, 3.9, 3.8, 4.1, 3.5, 3.8, 3.7, 3.9 and 3.4.
(i) Determine the range.
(ii) How many numbers are less than 3.5?
(iii) How many numbers are 3.8 or above?
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21A 6

Data Handling Exercise 21B – Selina Concise Mathematics Class 7 ICSE Solutions

Question 1.
Find the mean of 53, 61, 60, 67 and 64.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 7

Question 2.
Find the mean of first six natural numbers.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 8

Question 3.
Find the mean of first ten odd natural numbers.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 9

Question 4.
Find the mean of all factors of 10.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 10

Question 5.
Find the mean of x + 3, x + 5, x + 7, x + 9 and x + 11.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 11

Question 6.
If different values of variable x are 19.8,15.4,13.7,11.71,11.8, 12.6,12.8,18.6,20.5 and 2.1, find the mean.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 12

Question 7.
The mean of a certain number of observations is 32. Find the resulting mean, if each observation is,
(i) increased by 3
(ii) decreased by 7
(iii) multiplied by 2
(iv) divided by 0.5
(v) increased by 60%
(vi) decreased by 20%
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 13
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 14

Question 8.
The pocket expenses (per day) of Anuj, during a certain week, from monday to Saturday were ₹85.40, ₹88.00, ₹86.50, ₹84.75, ₹82.60 and ₹87.25. Find the mean pocket expenses per day.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 15

Question 9.
If the mean of 8, 10, 7, x + 2 and 6 is 9, find the value of x.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 16

Question 10.
Find the mean of first six multiples of 3.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 17

Question 11.
Find the mean of first five prime numbers.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 18

Question 12.
The mean of six numbers :x-5,x- 1, x, x + 2, x + 4 and x + 12 is 15. Find the mean of first four numbers.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 19

Question 13.
Find the mean of squares of first five whole numbers.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 20

Question 14.
If the mean of 6, 4, 7, p and 10 is 8, find the value of p.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 21

Question 15.
Find the mean of first six multiples of 5.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 22

Question 16.
The rainfall (in mm) in a city on 7 days of a certain week is recorded as follows
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B Q16
Find the total and average (mean) rainfall for the week.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 23

Question 17.
The mean of marks scored by 100 students was found to be 40, later on it was discovered that a score of 53 was misread as 83. Find the correct mean.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 24

Question 18.
The mean of five numbers is 27. If one number is excluded, the mean of remaining numbers is 25. Find the excluded number.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 25

Question 19.
The mean of 5 numbers is 27. If one new number is included, the new mean is 25. Find the included number.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 26

Question 20.
Mean of 5 numbers is 20 and mean of other 5 numbers is 30. Find the mean of all the 10 numbers taken together.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 27

Question 21.
Find the median of:
(i) 5,7, 9, 11, 15, 17,2, 23 and 19
(ii) 9, 3, 20, 13, 0, 7 and 10
(iii) 18, 19, 20, 23, 22, 20, 17, 19, 25 and 21
(iv) 3.6, 9.4, 3.8, 5.6, 6.5, 8.9, 2.7, 10.8, 15.6, 1.9 and 7.6.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 28
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 29

Question 22.
Find the mean and the mode for the following data :
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B Q22
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 30

Question 23.
Find the mode of:
(i) 5, 6, 9, 13, 6, 5, 6, 7, 6, 6, 3
(ii) 7, 7, 8, 10, 10, 11, 10, 13, 14
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 31

Question 24.
Find the mode of :
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B Q24
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 32

Question 25.
The heights (in cm) of 8 girls of a class are 140,142,135,133,137,150,148 and 138 respectively. Find the mean height of these girls and their median height.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 33

Question 26.
Find the mean, the median and the mode of:
(i) 12, 24, 24, 12, 30 and 12
(ii) 21, 24, 21, 6, 15, 18, 21, 45, 9, 6, 27 and 15.
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 34
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 35

Question 27.
The following table shows the market positions of some brands of soap.
Draw a suitable bar graph :
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B Q27
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 36

Question 28.
The birth rate per thousand of different countries over a particular period of time is shown below.
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B Q28
Solution:
Selina Concise Mathematics Class 7 ICSE Solutions Chapter 21 Data Handling Ex 21B 37

Selina Concise Mathematics Class 7 ICSE Solutions