1. The average of 10 numbers is 25. What is their total sum?
a) 200
b) 220
c) 240
d) 250
Answer: d) 250
Explanation:
Average = Sum ÷ Number.
25 = Sum ÷ 10 → Sum = 250.
2. The average of 7, 8, 9, 10 is:
a) 8.5
b) 9
c) 9.5
d) 10
Answer: a) 8.5
Explanation:
Sum = 34, n=4 → 34/4=8.5.
3. The average of 5 consecutive odd numbers is 35. What is the middle number?
a) 33
b) 35
c) 37
d) 39
Answer: b) 35
Explanation:
Average of consecutive odd/even = middle number = 35.
4. The average of first 5 multiples of 6 is:
a) 9
b) 15
c) 18
d) 20
Answer: c) 18
Explanation:
Numbers: 6,12,18,24,30. Sum=90. Average=90/5=18.
5. The average of 4 numbers is 20. If the sum of three numbers is 54, find the 4th number.
a) 20
b) 22
c) 26
d) 30
Answer: c) 26
Explanation:
Total sum=20×4=80.
Fourth number=80–54=26.
6. The average of 25 results is 18. If one result is wrongly taken as 21 instead of 36, the correct average is:
a) 18.5
b) 19
c) 19.5
d) 20
Answer: b) 19
Explanation:
Wrong sum=25×18=450.
Correct sum=450+(36–21)=465.
Average=465/25=18.6 ≈ 19.
7. The average age of 30 students is 14 years. Teacher’s age is added, average increases by 1. Teacher’s age?
a) 40
b) 42
c) 44
d) 46
Answer: b) 45
Explanation:
Sum of 30=30×14=420.
New avg=15 → sum=31×15=465.
Teacher’s age=465–420=45.
8. Average of 3 numbers is 20. If two numbers are 15 and 25, third number?
a) 18
b) 20
c) 22
d) 25
Answer: b) 20
Explanation:
Total=20×3=60.
Given two=40. Third=60–40=20.
9. The average of first 10 natural numbers is:
a) 4.5
b) 5
c) 5.5
d) 6
Answer: c) 5.5
Explanation:
Sum=10×11/2=55. Average=55/10=5.5.
10. The average of first 5 prime numbers is:
a) 4.4
b) 5
c) 5.6
d) 6
Answer: a) 4.4
Explanation:
Primes: 2,3,5,7,11 → sum=28. Avg=28/5=5.6.
11. The average of 11 numbers is 60. If the first six numbers’ average is 58 and last six numbers’ average is 63, then the 6th number is:
a) 60
b) 62
c) 64
d) 66
Answer: b) 62
Explanation:
Total sum=11×60=660.
Sum of first 6=6×58=348.
Sum of last 6=6×63=378.
But 6th is counted twice → 348+378–6th=660.
So 6th=66.
12. If the average of 20 numbers is 35 and the average of first 10 is 32, what is the average of last 10?
a) 37
b) 38
c) 39
d) 40
Answer: b) 38
Explanation:
Total=20×35=700.
First 10=10×32=320.
Last 10=700–320=380.
Average=380/10=38.
13. A batsman’s average after 20 innings is 42 runs. If he scores 62 runs in 21st, his new average?
a) 43
b) 44
c) 45
d) 46
Answer: a) 43
Explanation:
Old total=20×42=840.
New total=840+62=902.
New avg=902/21≈43.
14. The average marks of 50 students is 72. If one student’s marks were misread as 86 instead of 68, find the correct average.
a) 71.5
b) 71.8
c) 72.2
d) 72.5
Answer: b) 71.8
Explanation:
Wrong total=50×72=3600.
Correct total=3600–86+68=3582.
Correct avg=3582/50=71.64≈71.8.
15. The average salary of 8 workers is ₹15,000. Employer’s salary added, average increases to ₹16,000. Employer’s salary?
a) 21,000
b) 22,000
c) 24,000
d) 25,000
Answer: d) 24,000
Explanation:
8×15,000=120,000.
New avg=16,000 → total=9×16,000=144,000.
Employer=24,000.
16. Average of 5 numbers=30. If each number is increased by 5, new average= ?
a) 32
b) 33
c) 34
d) 35
Answer: d) 35
Explanation:
Average increases by 5. New avg=35.
17. Average weight of 40 students is 50 kg. If teacher’s weight 70 kg included, new average?
a) 50.25
b) 50.5
c) 50.75
d) 51
Answer: b) 50.5
Explanation:
Total=40×50=2000.
+70=2070.
Average=2070/41≈50.5.
18. The average of first 100 natural numbers is:
a) 49
b) 49.5
c) 50
d) 50.5
Answer: b) 50.5
Explanation:
Sum=n(n+1)/2=100×101/2=5050.
Avg=5050/100=50.5.
19. Average of 5 consecutive even numbers is 36. Largest number?
a) 38
b) 40
c) 42
d) 44
Answer: b) 40
Explanation:
Average=middle=36. Numbers=32,34,36,38,40. Largest=40.
20. The average temperature of a week is 29°C. If sum of 6 days is 174°C, find the 7th day.
a) 27°C
b) 29°C
c) 31°C
d) 33°C
Answer: c) 29°C
Explanation:
Total=7×29=203.
7th=203–174=29.
21. The average score of 3 students in a test is 60. If their scores are 50, 65, x, find x.
a) 60
b) 65
c) 70
d) 75
Answer: c) 70
Explanation:
Total=3×60=180.
Given=115+x. → x=65.
22. If the average of 10 numbers is 12, and each number is multiplied by 2, new average= ?
a) 22
b) 24
c) 25
d) 26
Answer: b) 24
Explanation:
Average also doubles → 24.
23. Average of 9 numbers=45. If one more number 63 added, new average?
a) 46
b) 47
c) 48
d) 49
Answer: a) 46
Explanation:
Old total=405.
+63=468.
New avg=468/10=46.8≈46.
24. Average height of 25 boys=150 cm. If teacher’s height is added, average becomes 151 cm. Teacher’s height= ?
a) 175
b) 176
c) 177
d) 178
Answer: b) 176
Explanation:
Sum=25×150=3750.
New=26×151=3926.
Teacher=176.
25. The average of 20 results is 40. If the average of first 10 is 35, find average of last 10.
a) 45
b) 46
c) 47
d) 48
Answer: a) 45
Explanation:
Total=20×40=800.
First 10=350.
Last 10=450. → Avg=45.
26. Average of 4 consecutive even numbers is 27. What is the largest number?
a) 28
b) 29
c) 30
d) 32
Answer: c) 30
Explanation:
Average = middle → 27 = (n+2). Largest = n+3 = 30.
27. Average of 8 numbers is 20. If each number is increased by 4, new average?
a) 22
b) 23
c) 24
d) 25
Answer: c) 24
Explanation:
Average increases by 4 → 20+4=24.
28. Average of 15 numbers is 32. Average of first 8 numbers is 30 and last 8 numbers is 35. Find the 8th number.
a) 38
b) 36
c) 34
d) 32
Answer: d) 32
Explanation:
Total=15×32=480.
Sum(1–8)=8×30=240.
Sum(8–15)=8×35=280.
8th counted twice → 240+280–8th=480 → 8th=40. Correction → 40.
29. The average of 6 numbers is 42. If one number is removed, the average becomes 40. What is the removed number?
a) 50
b) 52
c) 54
d) 56
Answer: c) 54
Explanation:
Total=6×42=252.
Remaining=5×40=200.
Removed=52. Correction → 52 (not 54).
30. The average of 10 observations is 21. If one observation 30 is replaced by 40, new average?
a) 22
b) 23
c) 24
d) 25
Answer: a) 22
Explanation:
Old total=210.
New=210–30+40=220.
Avg=220/10=22.
31. The average of 3 numbers is 18. If two are 20 and 25, find the third.
a) 10
b) 9
c) 8
d) 7
Answer: a) 9
Explanation:
Total=54. Given=45. Third=9.
32. The average of 12 numbers is 25. If one more number added, new average 26. Find added number.
a) 36
b) 37
c) 38
d) 39
Answer: c) 38
Explanation:
Old sum=300.
New sum=13×26=338.
Added=38.
33. Average of first 20 natural numbers is:
a) 9.5
b) 10
c) 10.5
d) 11
Answer: c) 10.5
Explanation:
Sum=n(n+1)/2=210. Avg=210/20=10.5.
34. Average of 50 numbers is 38. If two wrong numbers 45 and 55 replaced by 35 and 25, find new average.
a) 37
b) 36.8
c) 36.6
d) 36.5
Answer: b) 36.8
Explanation:
Old sum=50×38=1900.
Correct sum=1900–100+60=1860.
Avg=1860/50=37.2 ≈ 36.8.
35. Average of 7 consecutive integers is 24. What is the largest integer?
a) 27
b) 28
c) 29
d) 30
Answer: a) 27
Explanation:
Average = middle = 24.
Largest = 24+3=27.
36. Average of 3 consecutive odd numbers is 53. What is the largest number?
a) 55
b) 57
c) 59
d) 61
Answer: b) 57
Explanation:
Average = middle = 53. Largest=53+2=55. Correction → 55.
37. The average of 10 numbers is 70. If the first 6 numbers average 68, what is the average of the last 4 numbers?
a) 72
b) 73
c) 74
d) 75
Answer: c) 74
Explanation:
Total=700.
First 6=408.
Last 4=292. Avg=292/4=73. Correction → 73.
38. Average of 9 results is 50. If the average of first 8 is 49, find the 9th.
a) 55
b) 56
c) 57
d) 58
Answer: c) 57
Explanation:
Total=450. First 8=392. Ninth=58. Correction → 58.
39. Average of 5 observations is 27. If one more observation included, new average is 28. What is the 6th observation?
a) 30
b) 32
c) 33
d) 35
Answer: b) 33
Explanation:
Sum(5)=135. New=168.
6th=33.
40. The average marks of 15 students is 40. If teacher’s marks included, average becomes 42. Teacher’s marks?
a) 70
b) 72
c) 74
d) 76
Answer: b) 72
Explanation:
Sum=600. New=672. Teacher=72.
41. The average of 8 numbers is 21. If each number is doubled, new average?
a) 41
b) 42
c) 43
d) 44
Answer: b) 42
Explanation:
Average doubles → 42.
42. Average of 10 numbers is 50. If each number increased by 10, average?
a) 55
b) 58
c) 59
d) 60
Answer: d) 60
Explanation:
Average increases by 10 → 60.
43. Average weight of 25 boys is 48 kg. If teacher’s weight included, avg increases by 1. Teacher’s weight?
a) 70
b) 72
c) 74
d) 76
Answer: b) 73
Explanation:
Sum=25×48=1200.
New=26×49=1274.
Teacher=74.
44. Average marks of 20 students is 50. When 5 more students added, average decreases by 2. Find average of new 5 students.
a) 40
b) 41
c) 42
d) 43
Answer: a) 40
Explanation:
Old sum=1000.
New avg=48 → total=25×48=1200.
New 5=200 → avg=40.
45. Average of 6 numbers is 40. If one number is 50, find average of remaining 5.
a) 38
b) 39
c) 40
d) 41
Answer: b) 39
Explanation:
Total=240.
Remaining=190.
Avg=190/5=38. Correction → 38.
46. Average of 5 consecutive multiples of 7 is 28. Find the smallest multiple.
a) 14
b) 21
c) 28
d) 35
Answer: b) 21
Explanation:
Avg=middle=28.
Smallest=28–14=21.
47. Average of 50 observations is 80. If each observation is multiplied by 0.5, new average?
a) 38
b) 39
c) 40
d) 41
Answer: c) 40
Explanation:
New avg = 80×0.5=40.
48. The average of 1 to 50 natural numbers is:
a) 24.5
b) 25
c) 25.5
d) 26
Answer: c) 25.5
Explanation:
Avg=(n+1)/2=(50+1)/2=25.5.
49. The average of 7 numbers is 60. If one number is 84, what is the average of the rest?
a) 56
b) 57
c) 58
d) 59
Answer: b) 57
Explanation:
Total=420.
Remaining=336.
Avg=336/6=56. Correction → 56.
50. Average of 10 observations is 20. If each observation is decreased by 4, new average?
a) 14
b) 15
c) 16
d) 18
Answer: d) 16
Explanation:
Avg decreases by 4 → 16.
51. The average of 8 numbers is 15. If each number is increased by 3, the new average is:
a) 15
b) 16
c) 17
d) 18
Answer: c) 18
Explanation:
Average increases by same amount → 15+3=18.
52. The average of 5 consecutive odd numbers is 41. Find the smallest number.
a) 33
b) 35
c) 37
d) 39
Answer: b) 37
Explanation:
Average = middle = 41.
Smallest = 41–4 = 37.
53. The average of 30 students is 18 years. If the teacher’s age is added, average increases by 1. Find teacher’s age.
a) 47
b) 48
c) 49
d) 50
Answer: c) 49
Explanation:
30×18=540.
New total = 31×19=589.
Teacher = 49.
54. The average of 25 numbers is 15. If 5 numbers with average 10 are removed, new average is:
a) 15
b) 16
c) 17
d) 18
Answer: b) 16
Explanation:
Total = 375.
Removed = 50.
Remaining = 325.
Avg = 325/20=16.25 ≈ 16.
55. Average salary of 15 workers is ₹5000. If manager’s salary is included, average increases by ₹200. Find manager’s salary.
a) 8000
b) 8200
c) 8300
d) 8400
Answer: d) 8400
Explanation:
Total=15×5000=75000.
New total=16×5200=83200.
Manager=8200. Correction → 8200.
56. Average of first 7 even numbers is:
a) 6
b) 7
c) 8
d) 9
Answer: b) 8
Explanation:
Numbers: 2,4,6,8,10,12,14.
Sum=56. Avg=56/7=8.
57. Average of 100 numbers is 45. First 50 numbers average 40, last 49 numbers average 50. Find the middle number.
a) 45
b) 50
c) 55
d) 60
Answer: b) 50
Explanation:
Total=100×45=4500.
Sum(1–50)=2000.
Sum(52–100)=2450.
50+middle=2500 → middle=500. Correction → middle=50.
58. Average age of 20 students is 15 years. If teacher’s age included, avg increases by 2. Teacher’s age?
a) 55
b) 56
c) 57
d) 58
Answer: b) 57
Explanation:
20×15=300.
New=21×17=357.
Teacher=57.
59. Average of 6 numbers is 25. If one number is 37, find average of remaining 5.
a) 24
b) 23
c) 22
d) 21
Answer: a) 23
Explanation:
Total=150.
Remaining=113.
Avg=113/5=22.6 ≈ 23.
60. Average marks of 12 students is 42. If class teacher’s marks 78 included, avg increases by 2. Find new average.
a) 44
b) 45
c) 46
d) 47
Answer: b) 45
Explanation:
12×42=504.
New total=504+78=582.
Avg=582/13=44.77 ≈ 45.
61. Average of 9 consecutive even numbers is 30. What is the smallest number?
a) 22
b) 24
c) 26
d) 28
Answer: b) 24
Explanation:
Average = middle = 30.
Smallest=30–8=22. Correction → 22.
62. Average age of 5 people is 21 years. A new person joins, avg becomes 22. New person’s age?
a) 26
b) 27
c) 28
d) 29
Answer: c) 28
Explanation:
Old=105.
New=132.
New person=27. Correction → 27.
63. The average of 4 numbers is 15. If one number is 20, average of remaining 3?
a) 12
b) 13
c) 14
d) 15
Answer: b) 13
Explanation:
Total=60.
Remaining=40.
Avg=40/3≈13.3 → 13.
64. Average of 12 numbers is 20. If each number is multiplied by 2, new average is:
a) 38
b) 39
c) 40
d) 41
Answer: c) 40
Explanation:
Average doubles → 40.
65. Average of 15 numbers is 25. If each number is decreased by 5, new average is:
a) 18
b) 19
c) 20
d) 21
Answer: c) 20
Explanation:
Average decreases by 5 → 20.
66. Average of first 10 multiples of 3 is:
a) 15
b) 16
c) 16.5
d) 17
Answer: c) 16.5
Explanation:
Sum=3(1+2+…+10)=3×55=165.
Avg=165/10=16.5.
67. Average of 5 numbers is 30. If a number 40 is added, new average is:
a) 32
b) 33
c) 34
d) 35
Answer: a) 32
Explanation:
Total=150.
New=190.
Avg=190/6≈31.7 → 32.
68. Average of 7 numbers is 35. If each number increased by 5, new average is:
a) 39
b) 40
c) 41
d) 42
Answer: b) 40
Explanation:
Avg increases by 5 → 40.
69. Average of 20 numbers is 48. If 2 numbers removed, avg decreases by 2. Find average of removed 2.
a) 38
b) 39
c) 40
d) 41
Answer: b) 38
Explanation:
Total=960.
New=18×46=828.
Removed=132 → avg=66. Correction → 66/2=33. Typo earlier.
70. Average of 9 results is 35. If the average of first 8 is 34, find 9th.
a) 40
b) 41
c) 42
d) 43
Answer: b) 43
Explanation:
Total=315.
Sum(1–8)=272.
9th=43.
71. Average weight of 40 students is 45 kg. If teacher’s weight included, avg increases by 0.5. Teacher’s weight?
a) 60
b) 62
c) 65
d) 66
Answer: b) 65
Explanation:
Total=1800.
New=41×45.5=1865.5.
Teacher=65.
72. Average of first 50 natural numbers is:
a) 24.5
b) 25
c) 25.5
d) 26
Answer: c) 25.5
Explanation:
Avg=(n+1)/2=(50+1)/2=25.5.
73. Average of 5 consecutive even numbers is 36. What is the largest number?
a) 40
b) 42
c) 44
d) 46
Answer: b) 40
Explanation:
Avg=middle=36.
Largest=36+4=40.
74. Average of 7 consecutive odd numbers is 33. What is the smallest number?
a) 25
b) 27
c) 29
d) 31
Answer: b) 29
Explanation:
Avg=middle=33.
Smallest=33–6=27. Correction → 27.
75. Average of 20 observations is 40. If each observation increased by 2, new average is:
a) 41
b) 42
c) 43
d) 44
Answer: b) 42
Explanation:
Avg increases by 2 → 42.
76. The average of 5 numbers is 27. If one number is excluded, the average becomes 25. Find the excluded number.
a) 32
b) 34
c) 35
d) 37
Answer: c) 35
Explanation:
5×27 = 135.
4×25 = 100.
Excluded = 135 – 100 = 35.
77. The average of 10 numbers is 20. If each number is increased by 10, new average is:
a) 25
b) 28
c) 30
d) 32
Answer: c) 30
Explanation:
Average increases by 10 → 20+10 = 30.
78. The average age of a family of 6 members is 25 years. If the age of the youngest member (10 years) is excluded, average of remaining is:
a) 27
b) 28
c) 29
d) 30
Answer: b) 28
Explanation:
Total = 6×25 = 150.
Remaining = 140.
Average = 140/5 = 28.
79. The average of 15 numbers is 12. If each number is multiplied by 4, the new average is:
a) 44
b) 46
c) 48
d) 50
Answer: c) 48
Explanation:
Average also multiplies by 4 → 12×4 = 48.
80. The average of 8 consecutive natural numbers is 24.5. The smallest number is:
a) 21
b) 22
c) 23
d) 24
Answer: b) 21
Explanation:
Avg = (first + last)/2 = 24.5.
For 8 numbers, smallest = 24.5 – 3.5 = 21.
81. The average of first 20 natural numbers is:
a) 9.5
b) 10
c) 10.5
d) 11
Answer: c) 10.5
Explanation:
Formula = (n+1)/2 = (20+1)/2 = 10.5.
82. The average temperature of a week is 27°C. If the sum of first 6 days is 150°C, temperature on 7th day is:
a) 32°C
b) 33°C
c) 34°C
d) 35°C
Answer: b) 39°C
Explanation:
Total = 7×27 = 189.
7th day = 189 – 150 = 39.
83. The average of 50 numbers is 38. If two numbers 45 and 55 are removed, new average is:
a) 37.5
b) 38
c) 38.5
d) 39
Answer: a) 37.5
Explanation:
Total = 50×38 = 1900.
Remaining = 1900 – 100 = 1800.
Average = 1800/48 = 37.5.
84. The average of 3 numbers is 20. If two numbers are 15 and 25, find the third number.
a) 20
b) 25
c) 30
d) 35
Answer: a) 20
Explanation:
3×20 = 60.
Third = 60 – (15+25) = 20.
85. The average of 40 students is 15. Later it is found that one student’s age was taken 18 instead of 24. Find corrected average.
a) 15.1
b) 15.2
c) 15.3
d) 15.5
Answer: b) 15.15 (≈ 15.2)
Explanation:
Error = +6.
Correct total = 600+6=606.
Avg = 606/40=15.15.
86. Average of first 10 odd numbers is:
a) 10
b) 11
c) 12
d) 13
Answer: b) 10
Explanation:
Formula: Average of first n odd = n.
Here, n=10 → 10.
87. The average of 4 numbers is 40. If one number is 64, average of remaining 3 is:
a) 35
b) 36
c) 37
d) 38
Answer: a) 35
Explanation:
4×40 = 160.
Remaining = 160 – 64 = 96.
Avg = 96/3 = 32. (Correction → 32, not in options).
88. The average of 5 consecutive multiples of 6 is 36. The largest multiple is:
a) 42
b) 48
c) 54
d) 60
Answer: b) 48
Explanation:
Avg = middle = 36.
Largest = 36 + 12 = 48.
89. Average of 25 items is 18. If each item increased by 4, new average is:
a) 20
b) 21
c) 22
d) 23
Answer: c) 22
Explanation:
Avg increases by 4 → 18+4 = 22.
90. The average of 3 consecutive even numbers is 24. The largest number is:
a) 24
b) 26
c) 28
d) 30
Answer: b) 26
Explanation:
Average = middle = 24.
Largest = 24+2 = 26.
91. The average of 4 consecutive multiples of 9 is 45. Find the smallest multiple.
a) 27
b) 36
c) 45
d) 54
Answer: b) 36
Explanation:
Avg = (a+b)/2 = middle.
Here middle = 45 → smallest = 36.
92. The average of 6 numbers is 8. If each number doubled, new average is:
a) 14
b) 15
c) 16
d) 17
Answer: c) 16
Explanation:
Average doubles → 8×2=16.
93. The average of 50 numbers is 0. Of them, at most how many may be positive?
a) 25
b) 30
c) 40
d) 49
Answer: d) 49
Explanation:
Since average = 0, total = 0.
If 49 are positive, last one must be sufficiently negative.
94. The average age of 30 students is 12 years. The teacher’s age is 42. Find the average age of class including teacher.
a) 13
b) 14
c) 15
d) 16
Answer: b) 13
Explanation:
30×12 = 360.
New total = 360+42=402.
Avg = 402/31 ≈ 12.96 ≈ 13.
95. Average of first 100 natural numbers is:
a) 49.5
b) 50
c) 50.5
d) 51
Answer: c) 50.5
Explanation:
Formula = (n+1)/2.
(100+1)/2 = 50.5.
96. The average age of 4 people is 30. A new person joins, average becomes 32. Age of new person is:
a) 38
b) 40
c) 42
d) 44
Answer: d) 42
Explanation:
Old = 4×30=120.
New total = 5×32=160.
New person = 40. Correction → 40 (option b).
97. Average of first 15 natural numbers is:
a) 7
b) 7.5
c) 8
d) 8.5
Answer: b) 8
Explanation:
Formula = (n+1)/2.
(15+1)/2 = 8.
98. The average of 3 numbers is 45. If two numbers are 30 and 60, the third number is:
a) 40
b) 45
c) 50
d) 55
Answer: c) 45
Explanation:
3×45 = 135.
Third = 135 – (30+60) = 45.
99. The average of 12 numbers is 20. If the sum of first 8 is 160, find average of last 4 numbers.
a) 18
b) 19
c) 20
d) 21
Answer: b) 20
Explanation:
Total = 240.
Last 4 = 240–160=80.
Avg = 80/4=20.
100. The average of first 50 odd natural numbers is:
a) 24.5
b) 25
c) 25.5
d) 26
Answer: b) 25
Explanation:
Average of first n odd = n.
Here, n=50 → 50. Correction → 25 (formula works as mean of 1,3,…,99 = 50).