Practice Set 7.4

(1) Complete the following cumulative freuqency table:

Class
(Height in cm)
Frequency
(No. of students)
Less than type frequency
150 - 153 05 5
153 - 156 07 5 +     =     
156 - 159 15      + 15 =   
159 - 162 10      +      = 37
162 - 165 05 37 + 5 = 42
165 - 168 03      +      = 45

Solution:

The Completed table is given below:

Class
(Height in cm)
Frequency
(No. of students)
Less than type frequency
150 - 153 05 5
153 - 156 07 5 + 7  =  12 
156 - 159 15  12  + 15 = 27
159 - 162 10  27  +  10  = 37
162 - 165 05 37 + 5 = 42
165 - 168 03  42  +  3  = 45

(2) Complete the following Cumulative Frequency Table:

Class
(Monthly Income in ₹)
Frequency
(No. of individuals)
More than or equal to type cumulative frequency
1000 - 5000 45 ......
5000 - 10000 19 ......
10000 - 15000 16 ......
15000 - 20000 02 ......
20000 - 25000 05 ......
Total N = 87

Solution:

The completed table is given below:

Class
(Monthly Income in ₹)
Frequency
(No. of individuals)
More than or equal to type cumulative frequency
1000 - 5000 45 87
5000 - 10000 19 87 − 45 = 42
10000 - 15000 16 42 − 19 = 23
15000 - 20000 02 23 − 16 = 7
20000 - 25000 05 7 − 2 = 5
Total N = 87

(3) The data is given for 62 students in a certain class regarding their mathematics marks out of 100. Take the classes 0 - 10, 10 - 20 ... and prepare frequency distribution table and cumulative frequency table more than or equal to type.

55, 60, 81, 90, 45, 65, 45, 52, 30, 85, 20, 10, 75, 95, 09, 20, 25, 39, 45, 50, 78, 70, 46, 64, 42, 58, 31, 82, 27, 11, 78, 97, 07, 22, 27, 36, 35, 40, 75, 80, 47, 69, 48, 59, 32, 83, 23, 17, 77, 45, 05, 23, 37, 38, 35, 25, 46, 57, 68, 45, 47, 49

Solution:

The cumulative frequency table (More than or equal to type) is given below:

Class Tally Marks Frequency (f) Cumulative Frequency
(More than type)
0 - 10 \(|||\) 3 62
10 - 20 \(|||\) 3 62 − 3 = 59
20 - 30 \(\enclose{downdiagonalstrike}{||||} ||||\)  9  59 − 3 = 56
30 - 40 \(\enclose{downdiagonalstrike}{||||} ||||\)  9  56 − 9 = 47
40 - 50 \(\enclose{downdiagonalstrike}{||||}\enclose{downdiagonalstrike}{||||} |||\)  13  47 − 9 = 38
50 - 60 \(\enclose{downdiagonalstrike}{||||} |\)  6  38 − 13 = 25
60 - 70 \(\enclose{downdiagonalstrike}{||||}\)  5  25 − 6 = 19
70 - 80 \(\enclose{downdiagonalstrike}{||||} |\)  6  19 − 5 = 14
80 - 90 \(\enclose{downdiagonalstrike}{||||}\)  5  14 − 6 = 8
90 - 100 \(|||\)  3  8 − 5 = 3
\(\displaystyle N = \sum{f} = 62\)

Now, answer the following questions:

(i) How many students obtained 40 marks or above 40?
Answer: 38

(ii) How many students obtained marks 90 or above 90?
Answer: 3

(iii) How many students obtained marks 60 or above 60?
Answer: 19

(iv) What is the cumulative frequency of equal to or more than type of the class 0 - 10?
Answer: 62


(4) Using the data in example (3) above, prepare less than type cumulative frequency table and answer the following questions:

Solution:

The cumulative frequency table (Less than or equal to type) is given below:

Class Tally Marks Frequency (f) Cumulative Frequency
(Less than type)
0 - 10 \(|||\) 3 3
10 - 20 \(|||\) 6 3 + 3 = 6
20 - 30 \(\enclose{downdiagonalstrike}{||||} ||||\)  9  6 + 9 = 15
30 - 40 \(\enclose{downdiagonalstrike}{||||} ||||\)  9  15 + 9 = 24
40 - 50 \(\enclose{downdiagonalstrike}{||||}\enclose{downdiagonalstrike}{||||} |||\)  13  24 + 13 = 37
50 - 60 \(\enclose{downdiagonalstrike}{||||} |\)  6  37 + 6 = 43
60 - 70 \(\enclose{downdiagonalstrike}{||||}\)  5  43 + 5 = 48
70 - 80 \(\enclose{downdiagonalstrike}{||||} |\)  6  48 + 6 = 54
80 - 90 \(\enclose{downdiagonalstrike}{||||}\)  5  54 + 5 = 59
90 - 100 \(|||\)  3  59 + 3 = 62
\(\displaystyle N = \sum{f} = 62\)

Now, answer the following questions:

(i) How many students obtained less than 40 marks?
Answer: 24

(ii) How many students obtained less than 10 marks?
Answer: 3

(iii) How many students obtained less than 60 marks?
Answer: 43

(iv) Find the cumulative frequency of the class 50 - 60.
Answer: 43




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