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Data Handling – II (Central Values Exercise 23.2) RD Sharma Solutions | Mathematics (Maths) Class 7 PDF Download

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1. A die was thrown 20 times and the following scores were recorded: 
5, 2, 1, 3, 4, 4, 5, 6, 2, 2, 4, 5, 5, 6, 2, 2, 4, 5, 5, 1 
Prepare the frequency table of the scores on the upper face of the die and find the 
mean score. 
 
Solution: 
The frequency table for the given data is as follows: 
x: 1 2 3 4 5 6 
f: 2 5 1 4 6 2 
 
To compute arithmetic mean we have to prepare the following table: 
Scores (x
i
) Frequency (f
i
) x
i 
f
i 
1 2 2 
2 5 10 
3 1 3 
4 4 16 
5 6 30 
6 2 12 
Total S f
i
 = 20 S f
i 
x
i
 
 
Mean score = S f
i 
x
i
/ S f
i 
= 73/20  
= 3.65 
 
2. The daily wages (in Rs) of 15 workers in a factory are given below: 
200, 180, 150, 150, 130, 180, 180, 200, 150, 130, 180, 180, 200, 150, 180 
Prepare the frequency table and find the mean wage. 
 
Solution: 
Wages (x
i
) 130 150 180 200 
Number of workers (f
i
) 2 4 6 3 
 
To compute arithmetic mean we have to prepare the following table: 
 
Page 2


 
 
 
 
 
    
 
         
 
1. A die was thrown 20 times and the following scores were recorded: 
5, 2, 1, 3, 4, 4, 5, 6, 2, 2, 4, 5, 5, 6, 2, 2, 4, 5, 5, 1 
Prepare the frequency table of the scores on the upper face of the die and find the 
mean score. 
 
Solution: 
The frequency table for the given data is as follows: 
x: 1 2 3 4 5 6 
f: 2 5 1 4 6 2 
 
To compute arithmetic mean we have to prepare the following table: 
Scores (x
i
) Frequency (f
i
) x
i 
f
i 
1 2 2 
2 5 10 
3 1 3 
4 4 16 
5 6 30 
6 2 12 
Total S f
i
 = 20 S f
i 
x
i
 
 
Mean score = S f
i 
x
i
/ S f
i 
= 73/20  
= 3.65 
 
2. The daily wages (in Rs) of 15 workers in a factory are given below: 
200, 180, 150, 150, 130, 180, 180, 200, 150, 130, 180, 180, 200, 150, 180 
Prepare the frequency table and find the mean wage. 
 
Solution: 
Wages (x
i
) 130 150 180 200 
Number of workers (f
i
) 2 4 6 3 
 
To compute arithmetic mean we have to prepare the following table: 
 
 
 
 
 
 
    
 
x
i 
f
i 
x
i 
f
i
 
130 2 260 
150 4 600 
180 6 1080 
200 3 600 
Total S f
i
 = N = 15 S f
i 
x
i
 = 2540 
 
Mean score = S f
i 
x
i
/ S f
i 
= 2540/15 
= 169.33 
 
3. The following table shows the weights (in kg) of 15 workers in a factory: 
Weight (in Kg) 60 63 66 72 75 
Number of workers 4 5 3 1 2 
Calculate the mean weight. 
 
Solution: 
Calculation of mean: 
x
i
 f
i
 x
i 
f
i
 
60 4 240 
63 5 315 
66 3 198 
72 1 72 
75 2 150 
Total S f
i
 = N = 15 S f
i 
x
i
 = 975 
 
Mean score = S f
i 
x
i
/ S f
i 
= 975/15 
= 65 kg 
 
4. The ages (in years) of 50 students of a class in a school are given below: 
Age (in years) 14 15 16 17 18 
Number of students 15 14 10 8 3 
Find the mean age. 
 
Solution: 
Page 3


 
 
 
 
 
    
 
         
 
1. A die was thrown 20 times and the following scores were recorded: 
5, 2, 1, 3, 4, 4, 5, 6, 2, 2, 4, 5, 5, 6, 2, 2, 4, 5, 5, 1 
Prepare the frequency table of the scores on the upper face of the die and find the 
mean score. 
 
Solution: 
The frequency table for the given data is as follows: 
x: 1 2 3 4 5 6 
f: 2 5 1 4 6 2 
 
To compute arithmetic mean we have to prepare the following table: 
Scores (x
i
) Frequency (f
i
) x
i 
f
i 
1 2 2 
2 5 10 
3 1 3 
4 4 16 
5 6 30 
6 2 12 
Total S f
i
 = 20 S f
i 
x
i
 
 
Mean score = S f
i 
x
i
/ S f
i 
= 73/20  
= 3.65 
 
2. The daily wages (in Rs) of 15 workers in a factory are given below: 
200, 180, 150, 150, 130, 180, 180, 200, 150, 130, 180, 180, 200, 150, 180 
Prepare the frequency table and find the mean wage. 
 
Solution: 
Wages (x
i
) 130 150 180 200 
Number of workers (f
i
) 2 4 6 3 
 
To compute arithmetic mean we have to prepare the following table: 
 
 
 
 
 
 
    
 
x
i 
f
i 
x
i 
f
i
 
130 2 260 
150 4 600 
180 6 1080 
200 3 600 
Total S f
i
 = N = 15 S f
i 
x
i
 = 2540 
 
Mean score = S f
i 
x
i
/ S f
i 
= 2540/15 
= 169.33 
 
3. The following table shows the weights (in kg) of 15 workers in a factory: 
Weight (in Kg) 60 63 66 72 75 
Number of workers 4 5 3 1 2 
Calculate the mean weight. 
 
Solution: 
Calculation of mean: 
x
i
 f
i
 x
i 
f
i
 
60 4 240 
63 5 315 
66 3 198 
72 1 72 
75 2 150 
Total S f
i
 = N = 15 S f
i 
x
i
 = 975 
 
Mean score = S f
i 
x
i
/ S f
i 
= 975/15 
= 65 kg 
 
4. The ages (in years) of 50 students of a class in a school are given below: 
Age (in years) 14 15 16 17 18 
Number of students 15 14 10 8 3 
Find the mean age. 
 
Solution: 
 
 
 
 
 
    
 
Calculation of mean: 
 
x
i
 f
i
 x
i 
f
i
 
14 15 210 
15 14 210 
16 10 160 
17 8 136 
18 3 54 
Total S f
i
 = N = 50 S f
i 
x
i
 = 770 
 
Mean score = S f
i 
x
i
/ S f
i 
= 770/50 
= 15.4 years 
 
5. Calculate the mean for the following distribution: 
x: 5 6 7 8 9 
f: 4 8 14 11 3 
 
Solution: 
x
i
 f
i
 x
i 
f
i
 
5 4 20 
6 8 48 
7 14 98 
8 11 88 
9 3 27 
Total S f
i
 = N = 40 S f
i 
x
i
 = 281 
 
Mean score = S f
i 
x
i
/ S f
i 
= 281/40 
= 7.025 
 
6. Find the mean of the following data: 
x: 19 21 23 25 27 29 31 
f: 13 15 16 18 16 15 13 
 
Solution: 
Page 4


 
 
 
 
 
    
 
         
 
1. A die was thrown 20 times and the following scores were recorded: 
5, 2, 1, 3, 4, 4, 5, 6, 2, 2, 4, 5, 5, 6, 2, 2, 4, 5, 5, 1 
Prepare the frequency table of the scores on the upper face of the die and find the 
mean score. 
 
Solution: 
The frequency table for the given data is as follows: 
x: 1 2 3 4 5 6 
f: 2 5 1 4 6 2 
 
To compute arithmetic mean we have to prepare the following table: 
Scores (x
i
) Frequency (f
i
) x
i 
f
i 
1 2 2 
2 5 10 
3 1 3 
4 4 16 
5 6 30 
6 2 12 
Total S f
i
 = 20 S f
i 
x
i
 
 
Mean score = S f
i 
x
i
/ S f
i 
= 73/20  
= 3.65 
 
2. The daily wages (in Rs) of 15 workers in a factory are given below: 
200, 180, 150, 150, 130, 180, 180, 200, 150, 130, 180, 180, 200, 150, 180 
Prepare the frequency table and find the mean wage. 
 
Solution: 
Wages (x
i
) 130 150 180 200 
Number of workers (f
i
) 2 4 6 3 
 
To compute arithmetic mean we have to prepare the following table: 
 
 
 
 
 
 
    
 
x
i 
f
i 
x
i 
f
i
 
130 2 260 
150 4 600 
180 6 1080 
200 3 600 
Total S f
i
 = N = 15 S f
i 
x
i
 = 2540 
 
Mean score = S f
i 
x
i
/ S f
i 
= 2540/15 
= 169.33 
 
3. The following table shows the weights (in kg) of 15 workers in a factory: 
Weight (in Kg) 60 63 66 72 75 
Number of workers 4 5 3 1 2 
Calculate the mean weight. 
 
Solution: 
Calculation of mean: 
x
i
 f
i
 x
i 
f
i
 
60 4 240 
63 5 315 
66 3 198 
72 1 72 
75 2 150 
Total S f
i
 = N = 15 S f
i 
x
i
 = 975 
 
Mean score = S f
i 
x
i
/ S f
i 
= 975/15 
= 65 kg 
 
4. The ages (in years) of 50 students of a class in a school are given below: 
Age (in years) 14 15 16 17 18 
Number of students 15 14 10 8 3 
Find the mean age. 
 
Solution: 
 
 
 
 
 
    
 
Calculation of mean: 
 
x
i
 f
i
 x
i 
f
i
 
14 15 210 
15 14 210 
16 10 160 
17 8 136 
18 3 54 
Total S f
i
 = N = 50 S f
i 
x
i
 = 770 
 
Mean score = S f
i 
x
i
/ S f
i 
= 770/50 
= 15.4 years 
 
5. Calculate the mean for the following distribution: 
x: 5 6 7 8 9 
f: 4 8 14 11 3 
 
Solution: 
x
i
 f
i
 x
i 
f
i
 
5 4 20 
6 8 48 
7 14 98 
8 11 88 
9 3 27 
Total S f
i
 = N = 40 S f
i 
x
i
 = 281 
 
Mean score = S f
i 
x
i
/ S f
i 
= 281/40 
= 7.025 
 
6. Find the mean of the following data: 
x: 19 21 23 25 27 29 31 
f: 13 15 16 18 16 15 13 
 
Solution: 
 
    
x
i
 f
i
 x
i 
f
i
 
19 13 247 
21 15 315 
23 16 368 
25 18 450 
27 16 432 
29 15 435 
31 13 403 
Total S f
i
 = N = 106 S f
i 
x
i
 = 2650 
Mean score = S f
i 
x
i
/ S f
i
= 2650/106 
= 25 
7. The mean of the following data is 20.6. Find the value of p.
x: 10 15 p 25 3 5 
f: 3 10 25 7 5 
Solution: 
x
i
 f
i
 x
i 
f
i
 
10 3 30 
15 10 150 
P 25 25p 
25 7 175 
3 5 5 175 
Total S f
i
 = N = 50 S f
i 
x
i
 = 530 + 25p 
Mean score = S f
i 
x
i
/ S f
i
20.6 = 530 + 25p/50 
530 + 25 p = 20.6 x 50 
25 p = 1030 – 530 
p = 500/25 
p = 20 
8. If the mean of the following data is 15, find p.
Page 5


 
 
 
 
 
    
 
         
 
1. A die was thrown 20 times and the following scores were recorded: 
5, 2, 1, 3, 4, 4, 5, 6, 2, 2, 4, 5, 5, 6, 2, 2, 4, 5, 5, 1 
Prepare the frequency table of the scores on the upper face of the die and find the 
mean score. 
 
Solution: 
The frequency table for the given data is as follows: 
x: 1 2 3 4 5 6 
f: 2 5 1 4 6 2 
 
To compute arithmetic mean we have to prepare the following table: 
Scores (x
i
) Frequency (f
i
) x
i 
f
i 
1 2 2 
2 5 10 
3 1 3 
4 4 16 
5 6 30 
6 2 12 
Total S f
i
 = 20 S f
i 
x
i
 
 
Mean score = S f
i 
x
i
/ S f
i 
= 73/20  
= 3.65 
 
2. The daily wages (in Rs) of 15 workers in a factory are given below: 
200, 180, 150, 150, 130, 180, 180, 200, 150, 130, 180, 180, 200, 150, 180 
Prepare the frequency table and find the mean wage. 
 
Solution: 
Wages (x
i
) 130 150 180 200 
Number of workers (f
i
) 2 4 6 3 
 
To compute arithmetic mean we have to prepare the following table: 
 
 
 
 
 
 
    
 
x
i 
f
i 
x
i 
f
i
 
130 2 260 
150 4 600 
180 6 1080 
200 3 600 
Total S f
i
 = N = 15 S f
i 
x
i
 = 2540 
 
Mean score = S f
i 
x
i
/ S f
i 
= 2540/15 
= 169.33 
 
3. The following table shows the weights (in kg) of 15 workers in a factory: 
Weight (in Kg) 60 63 66 72 75 
Number of workers 4 5 3 1 2 
Calculate the mean weight. 
 
Solution: 
Calculation of mean: 
x
i
 f
i
 x
i 
f
i
 
60 4 240 
63 5 315 
66 3 198 
72 1 72 
75 2 150 
Total S f
i
 = N = 15 S f
i 
x
i
 = 975 
 
Mean score = S f
i 
x
i
/ S f
i 
= 975/15 
= 65 kg 
 
4. The ages (in years) of 50 students of a class in a school are given below: 
Age (in years) 14 15 16 17 18 
Number of students 15 14 10 8 3 
Find the mean age. 
 
Solution: 
 
 
 
 
 
    
 
Calculation of mean: 
 
x
i
 f
i
 x
i 
f
i
 
14 15 210 
15 14 210 
16 10 160 
17 8 136 
18 3 54 
Total S f
i
 = N = 50 S f
i 
x
i
 = 770 
 
Mean score = S f
i 
x
i
/ S f
i 
= 770/50 
= 15.4 years 
 
5. Calculate the mean for the following distribution: 
x: 5 6 7 8 9 
f: 4 8 14 11 3 
 
Solution: 
x
i
 f
i
 x
i 
f
i
 
5 4 20 
6 8 48 
7 14 98 
8 11 88 
9 3 27 
Total S f
i
 = N = 40 S f
i 
x
i
 = 281 
 
Mean score = S f
i 
x
i
/ S f
i 
= 281/40 
= 7.025 
 
6. Find the mean of the following data: 
x: 19 21 23 25 27 29 31 
f: 13 15 16 18 16 15 13 
 
Solution: 
 
    
x
i
 f
i
 x
i 
f
i
 
19 13 247 
21 15 315 
23 16 368 
25 18 450 
27 16 432 
29 15 435 
31 13 403 
Total S f
i
 = N = 106 S f
i 
x
i
 = 2650 
Mean score = S f
i 
x
i
/ S f
i
= 2650/106 
= 25 
7. The mean of the following data is 20.6. Find the value of p.
x: 10 15 p 25 3 5 
f: 3 10 25 7 5 
Solution: 
x
i
 f
i
 x
i 
f
i
 
10 3 30 
15 10 150 
P 25 25p 
25 7 175 
3 5 5 175 
Total S f
i
 = N = 50 S f
i 
x
i
 = 530 + 25p 
Mean score = S f
i 
x
i
/ S f
i
20.6 = 530 + 25p/50 
530 + 25 p = 20.6 x 50 
25 p = 1030 – 530 
p = 500/25 
p = 20 
8. If the mean of the following data is 15, find p.
 
 
 
 
 
    
 
x: 5 10 15 20 25 
f: 6 p 6 10 5 
 
Solution: 
                
x
i
 f
i
 x
i 
f
i
 
5 6 30 
10 P 10p 
15 6 90 
20 10 200 
25 5 125 
Total S f
i
 = 27 + p S f
i 
x
i
 = 445 + 10p 
 
Mean score = S f
i 
x
i
/ S f
i 
15 = 445 + 10p/27 + p 
445 + 10 p = 405 + 15p 
5 p = 445 – 405 
p = 40/5 
p = 8 
 
9. Find the value of p for the following distribution whose mean is 16.6 
x: 8 12 15 p 20 25 30 
f: 12 16 20 24 16 8 4 
 
Solution: 
x
i
 f
i
 x
i 
f
i
 
8 12 96 
12 16 192 
15 20 300 
P 24 24p 
20 16 320 
25 8 200 
30 4 120 
Total S f
i
 = N = 100 S f
i 
x
i
 = 1228 + 24p 
 
Mean score = S f
i 
x
i
/ S f
i 
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