1) If 7 is the mean of 5, 3 0.5, 4.5, b, 8.5, 9.5, find b. 18
2) If each Observation is decreased by 1 unit, what would the new mean be ? 6
3) if the mean of 6, 8,5,4,7 and X is 7. Find X. 12
4) Find mean of:
A) first ten natural numbers. 5.5
B) first five prime numbers. 5.6
C) first 8 even natural numbers. 9
D) All the factors of 20. 7
E) 76 ,44, 45, 71, 87, 41, 83 , 82, 32 ,72, 32 ,46, 75 ,78, 17, 70, 74, 77 , 84, 12. 59.9
F) 7, 12, 21, 9 ,11, 14, 16 ,19,20, 25,12, 2 . 14
G) 5.8, 6.3, 7.1 , 9.4, 4.9 . 6.7
H) 2.6, 1.9, 7.2, 4.6 ,5. 8, 3.7. 4.3
5) The mean weight of 60 students of a class is 52.75 kg. If the mean weight of 25 of them is 51kg, find the mean weight of the remaining students. 54
6) The mean of 70 observations was found to be 150. While checking, it was detected that one value 210 was wrongly copied as 140 while calculating the mean. Find the correct mean. 151
7) The marks obtained by 10 students in a test are 6,5,8,0, 7, 9,.3, 1, 5, 4 . Find
A) the mean of their marks. 4.9
B) the mean of their marks, when the marks of each student are increased by 3. 7.9
8) the mean of 5 numbers is 18. On excluding one number, the mean becomes 16. Find the excluded number. 26
9) Find the mean of the following:
a) Marks: 5 10 15 20 25 30
No.of boys: 6 4 6 12 x 4 8
b) Variate: 5 6 7 8 9
Frequency: 4 5 3 6 2 6.85
c) X: 3 4 5 6 7 8
F: 4 6 20 34 20 10 6.02
d) Salary No of persons
400 10
600 8
800 6
1000 10
1200 10
1500 6 892
e) x: 12 13 14 15 16 17
f: 6 2 5 p 9 5
If mean is 14.5 then find p. 7
f) x: 10 12 14 16 18
f: 4 5 14 p 3 If mean is 14 find p. 7
g) Class-interval Frequency
00-50 4
50-100 8
100-150 16
150-200 13
200-250 6
250-300 3 143
h) Class- interval frequency
80-100 20
100-120 30
120-140 20
140-160 40
160-180 90. 145
i) Marks obtained No.of students
10-20 2
20-30 4
30-40 5
40-50 16
50-60 20
60-70 10
70-80 6
80-90 8
90-100 4 57.1
j) No.of words frequency
1-3 3
4-6 36
7-9 49
10-12 28
13-15 4 7.85
k) Weight frequency
80-84 2
85-89 6
90-94 12
95-99 14
100-104 10
105-109 5
110-114 1 96
l)weekly wages(₹) No.of workers
Below 10 8
Below 20 18
Below 30 45
Below 40 90
Below 50 113
Below 60 120 32.17
m) Marks No. of students
More than 0 60
More than 10 56
More than 20 40
More than 30 20
More than 40 10
More than 50 3 26.5
o) Value No. of boys
Under ₹10 245
₹10 Under ₹20 383
₹20 Under ₹30 205
₹30 Under ₹40 89
₹40 Under ₹50 47
₹50 Under ₹60 21
₹60 Under ₹70 10
Find i) the total turnover b) the mean value of a single order. ₹19130, ₹19.13, ₹16.67
p) The mean of the following is 20.5. find the missing frequency.
X: 10 15 20 25 30
F: 5 7 -- 12 6 40
q) The mean of the following frequency table is 50. But the frequency a and b in classes 20-40 and 60-80 are missing. Find the missing frequencies.
Class Frequency
0 - 20 19
20 - 40 a
40 - 60 32
60 - 80 b
80 - 100 19 28, 24
r) The A. M calculated from the following frequency distribution is known to be 67.45 inches. Find the value of a.
Height (inches) frequency
60 - 62 15
63 - 65 54
66 - 68 a
69 - 71 81
72 - 74 24 126
10) Using Short-cut Method find mean :
a) Height : 58 60 62 65 66 68
Frequency: 15 14 20 18 8 5 . 62.35
b) Class Frequency
50-55 8
55-60 10
60-65 12
65-70 8
70-75 10
75-80 3 65.48
c) Class Frequency
35-40 7
40-45 6
45-50 9
50-55 5
55-60 3 46
11) Using Step-deviation method, calculate the mean of the following:
a) Marks No of students
00-10 2
10-20 8
20-30 15
30-40 21
40-50 4
50-60 52
60-70 37
70-80 21
80-90 15
90-100 5 55.61
b)weekly income(in₹) no workers
30-40 8
40-50 7
50-60 10
60-70 15
70-80 5
80-90 8
90-100 7 64
c) Greater than/equal to No.
0 100
10 90
20 75
30 50
40 25
50 15
60 5
70 0. 31
d) class interval frequency
135-140 4
140-145 9
145-150 18
150-155 28
155-160 24
160-165 10
165-170 5
170-175 2 153.45
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