Selina solutions concise mathematica class 7 icse Solutions for Chapter 21 data handling

Exercises in Chapter 21 data handling Grade 7

Exercise 21(A)

Exercise 21(B)

Questions in Exercise 21(A)

Q1) 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 is the range of these numbers?

Q2) 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.

Q3) A die was thrown 20 times and the 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.

Q4) Following data shows the weekly wages (in Rs.) 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 Rs.)?

(iii) How many workers are getting maximum wages?

Q5) 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?

Q6) 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?

Questions in Exercise 21(B)

Q1) Find the mean of 53, 61, 60, 67 and 64.

Q2) Find the mean of the first six natural numbers.

Q3) Find the mean of first ten odd natural numbers.

Q4) Find the mean of all factors of 10.

Q5) Find the mean of x + 3, x + 5, x + 7, x + 9 and x + 11.

Q6) 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.

Q7) 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%

Q8) The pocket expenses (per day) of Anuj, during a certain week, from Monday to Saturday were Rs. 85.40, Rs. 88.00, Rs. 86.50, Rs. 84.75, Rs. 82.60 and Rs. 87.25. Find the mean pocket expenses per day.

Q9) If the mean of 8, 10, 7, x + 2 and 6 is 9, find the value of x.

Q10) Find the mean of first six multiples of 3.

Q11) Find the mean of first five prime numbers.

Q12) 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.

Q13) Find the mean of squares of first five whole numbers.

Q14) If the mean of 6, 4, 7, p and 10 is 8, find the value of p

Q15) Find the mean of first six multiples of 5.

Q16) The rainfall (in mm) in a city on 7 days of a certain week is recorded as follows

Day	Rainfall (in mm)
Mon	0.5
Tue	2.7
Wed	2.6
Thus	0.5
Fri	2
Sat	5.8
Sun	1.5

Q17) 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.

Q18) The mean of five numbers is 27. If one number is excluded, the mean of remaining numbers is 25. Find the excluded number.

Q19) The mean of 5 numbers is 27. If one new number is included, the new mean is 25. Find the included number.

Q19)The mean of 5 numbers is 27. If one new number is included, the new mean is 25. Find the included number.

Q20) Mean of 5 numbers is 20 and mean of other 5 numbers is 30. Find the mean of all the 10 numbers taken together.

Q21) 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.

Q21) 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.

Q22) Find the mean and the mode for the following data:

Q22)Find the mean and the mode for the following data:

Term	Frequency
18	3
22	5
26	10
30	2
34	8
38	2

Q23) 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

Q23)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

Q24) Find the mode of :

Q25)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.

Q25) 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.

Q26) 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.

Q26)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.

Q27) The following table shows the market positions of some brands of soap.

Draw a suitable bar graph :

Q27)The following table shows the market positions of some brands of soap.

Draw a suitable bar graph :

Q28)The birth rate per thousand of different countries over a particular period of time is shown below.

Draw a suitable bar graph :