20 Average Aptitude Questions with Answers
20 Average Aptitude Questions with Answers
Average is a fundamental topic in quantitative aptitude and is commonly tested in placement tests, competitive examinations, entrance tests, and recruitment assessments. Average questions may involve marks, ages, salaries, scores, temperatures, production, expenditure, and many other real-life quantities.
This practice set contains 20 original Average Aptitude Questions with answers and detailed solutions. The questions begin with basic averages and gradually move toward replacement, combined-average, and missing-value problems.
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Try to solve all 20 questions before checking the answers.
Detailed answers and solutions are provided after Question 20.
Average Aptitude Test
Question 1
What is the average of 18, 24, 30, 36, and 42?
A. 28
B. 30
C. 32
D. 34
Question 2
The average of 8 numbers is 25. What is the sum of the numbers?
A. 180
B. 190
C. 200
D. 225
Question 3
The average marks obtained by a student in 5 subjects are 72. What are the total marks obtained?
A. 340
B. 350
C. 360
D. 370
Question 4
The average of 6 numbers is 18. If another number, 25, is added to the group, what is the new average?
A. 18
B. 19
C. 20
D. 21
Question 5
The average age of 4 friends is 24 years. If another friend aged 29 years joins them, what is the new average age?
A. 24 years
B. 25 years
C. 26 years
D. 27 years
Question 6
The average of five consecutive odd numbers is 37. What is the smallest number?
A. 31
B. 33
C. 35
D. 37
Question 7
The average of 7 numbers is 42. If one of the numbers, 54, is removed, what is the average of the remaining 6 numbers?
A. 38
B. 39
C. 40
D. 41
Question 8
Juhi scored an average of 68 marks in 4 tests. What score must she obtain in the fifth test to increase her average to 72?
A. 82
B. 84
C. 86
D. 88
Question 9
The average monthly salary of 12 employees is ₹32,000. If the manager’s salary is included, the average of all 13 people becomes ₹34,000. What is the manager’s salary?
A. ₹52,000
B. ₹54,000
C. ₹56,000
D. ₹58,000
Question 10
The average of 10 numbers is 46. Later, it is discovered that 64 was incorrectly recorded as 46. What is the correct average?
A. 46.8
B. 47.2
C. 47.8
D. 48.0
Question 11
The average age of 20 students is 18 years. If a teacher is included, the average age becomes 19 years. What is the teacher’s age?
A. 36 years
B. 38 years
C. 39 years
D. 40 years
Question 12
The average of 9 numbers is 34. The average of the first 5 numbers is 30. What is the average of the remaining 4 numbers?
A. 37
B. 38
C. 39
D. 40
Question 13
The average temperature from Monday to Wednesday is 30°C, and the average temperature from Thursday to Sunday is 33°C. What is the average temperature for the entire week?
A. 31°C
B. (31\frac{5}{7})°C
C. 32°C
D. (32\frac{2}{7})°C
Question 14
The average of 15 numbers is 28. If each number is increased by 6, what will be the new average?
A. 30
B. 32
C. 34
D. 36
Question 15
The average of 6 numbers is 35. If one number, 20, is replaced by 44, what is the new average?
A. 37
B. 38
C. 39
D. 40
Question 16
The average age of 30 students is 16 years. The average age of 18 of them is 15 years. What is the average age of the remaining 12 students?
A. 16.5 years
B. 17 years
C. 17.5 years
D. 18 years
Question 17
The average of 11 numbers is 50. The average of the first 6 numbers is 46, and the average of the last 6 numbers is 55. What is the sixth number?
A. 50
B. 52
C. 54
D. 56
Question 18
The average weight of 8 people increases by 2.5 kg when one person weighing 56 kg is replaced by another person. What is the weight of the new person?
A. 72 kg
B. 74 kg
C. 76 kg
D. 78 kg
Question 19
The average of 20 observations is 48. If the average of the first 12 observations is 44, what is the average of the remaining 8 observations?
A. 52
B. 53
C. 54
D. 55
Question 20
The average salary of 24 employees is ₹28,000. Four new employees, each earning ₹35,000, join the organization. What is the new average salary?
A. ₹28,500
B. ₹29,000
C. ₹30,000
D. ₹31,000
Answers and Detailed Solutions
Answer 1: B — 30
The average is calculated as:
[
\text{Average}=
\frac{\text{Sum of Observations}}
{\text{Number of Observations}}
]
First find the sum:
[
18+24+30+36+42=150
]
Number of observations:
[
5
]
Therefore:
[
\text{Average}=\frac{150}{5}=30
]
Correct Answer: 30
Answer 2: C — 200
We know:
[
\text{Sum}=\text{Average}\times\text{Number of Observations}
]
Therefore:
[
25\times8=200
]
Correct Answer: 200
Answer 3: C — 360
Average marks:
72
Number of subjects:
5
Total marks:
[
72\times5=360
]
Therefore:
Correct Answer: 360
Answer 4: B — 19
Average of 6 numbers:
18
Their total is:
[
18\times6=108
]
A new number, 25, is added.
New total:
[
108+25=133
]
There are now 7 numbers.
New average:
[
\frac{133}{7}=19
]
Therefore:
Correct Answer: 19
Answer 5: B — 25 years
Average age of 4 friends:
24 years
Their total age:
[
24\times4=96
]
Another friend aged 29 joins.
New total age:
[
96+29=125
]
Number of people:
5
New average:
[
\frac{125}{5}=25
]
Therefore:
Correct Answer: 25 years
Answer 6: B — 33
For five consecutive odd numbers, the middle number is also their average.
Average:
37
Therefore, the numbers are:
[
33,\ 35,\ 37,\ 39,\ 41
]
The smallest number is:
33
Therefore:
Correct Answer: 33
Answer 7: C — 40
Average of 7 numbers:
42
Total:
[
42\times7=294
]
Remove 54:
[
294-54=240
]
Remaining numbers:
6
New average:
[
\frac{240}{6}=40
]
Therefore:
Correct Answer: 40
Answer 8: D — 88
Juhi’s average in 4 tests is 68.
Total marks in 4 tests:
[
68\times4=272
]
She wants an average of 72 after 5 tests.
Required total:
[
72\times5=360
]
Required fifth-test score:
[
360-272=88
]
Therefore:
Correct Answer: 88
Answer 9: D — ₹58,000
Average salary of 12 employees:
₹32,000
Total salary:
[
12\times32000=₹384000
]
After including the manager:
Number of people = 13
New average = ₹34,000
New total salary:
[
13\times34000=₹442000
]
Manager’s salary:
[
442000-384000=58000
]
Therefore:
Correct Answer: ₹58,000
Answer 10: C — 47.8
The incorrect average of 10 numbers is 46.
Incorrect total:
[
46\times10=460
]
The number 64 was recorded as 46.
Difference:
[
64-46=18
]
Correct total:
[
460+18=478
]
Correct average:
[
\frac{478}{10}=47.8
]
Therefore:
Correct Answer: 47.8
Answer 11: C — 39 years
Average age of 20 students:
18 years
Total age of students:
[
20\times18=360
]
After including the teacher:
21 people have an average age of 19 years.
New total age:
[
21\times19=399
]
Teacher’s age:
[
399-360=39
]
Therefore:
Correct Answer: 39 years
Answer 12: C — 39
Average of all 9 numbers:
34
Total:
[
9\times34=306
]
Average of first 5 numbers:
30
Their total:
[
5\times30=150
]
Total of remaining 4 numbers:
[
306-150=156
]
Average:
[
\frac{156}{4}=39
]
Therefore:
Correct Answer: 39
Answer 13: B — (31\frac{5}{7})°C
Monday to Wednesday:
3 days × 30°C average
Total:
[
3\times30=90
]
Thursday to Sunday:
4 days × 33°C average
Total:
[
4\times33=132
]
Total for seven days:
[
90+132=222
]
Weekly average:
[
\frac{222}{7}
31\frac{5}{7}
]
Therefore:
Correct Answer: (31\frac{5}{7})°C
Notice that we cannot simply calculate:
[
\frac{30+33}{2}
]
because the two averages represent groups of different sizes.
Answer 14: C — 34
Original average:
28
Every number is increased by:
6
When the same value is added to every observation, the average increases by the same amount.
Therefore:
[
28+6=34
]
Correct Answer: 34
Answer 15: C — 39
Average of 6 numbers:
35
Original total:
[
35\times6=210
]
The number 20 is removed:
[
210-20=190
]
Replace it with 44:
[
190+44=234
]
New average:
[
\frac{234}{6}=39
]
Therefore:
Correct Answer: 39
Answer 16: C — 17.5 years
Average age of 30 students:
16 years
Total age:
[
30\times16=480
]
Average age of 18 students:
15 years
Their total age:
[
18\times15=270
]
Total age of remaining 12 students:
[
480-270=210
]
Average:
[
\frac{210}{12}=17.5
]
Therefore:
Correct Answer: 17.5 years
Answer 17: C — 54
Average of all 11 numbers:
50
Total:
[
11\times50=550
]
Average of first 6 numbers:
46
Their total:
[
6\times46=276
]
Average of last 6 numbers:
55
Their total:
[
6\times55=330
]
Notice that the sixth number occurs in both groups.
Therefore:
[
276+330=606
]
This counts the sixth number twice.
The total of all 11 numbers is 550.
Therefore, the sixth number is:
[
606-550=56
]
So the correct value is:
56
Correct Answer: D — 56
Answer 18: C — 76 kg
Average weight increases by:
2.5 kg
Number of people:
8
Therefore, total weight increases by:
[
8\times2.5=20\text{ kg}
]
The person who left weighed:
56 kg
Therefore, the new person’s weight is:
[
56+20=76
]
Therefore:
Correct Answer: 76 kg
Answer 19: C — 54
Average of 20 observations:
48
Total:
[
20\times48=960
]
Average of first 12 observations:
44
Their total:
[
12\times44=528
]
Total of remaining 8:
[
960-528=432
]
Average of remaining observations:
[
\frac{432}{8}=54
]
Therefore:
Correct Answer: 54
Answer 20: B — ₹29,000
Average salary of 24 employees:
₹28,000
Original total salary:
[
24\times28000=₹672000
]
Four new employees each earn ₹35,000.
Their total salary:
[
4\times35000=₹140000
]
New total salary:
[
672000+140000=₹812000
]
Total employees:
[
24+4=28
]
New average:
[
\frac{812000}{28}=₹29000
]
Therefore:
Correct Answer: ₹29,000
Quick Answer Key
| Question | Answer | Question | Answer |
|---|---|---|---|
| 1 | B | 11 | C |
| 2 | C | 12 | C |
| 3 | C | 13 | B |
| 4 | B | 14 | C |
| 5 | B | 15 | C |
| 6 | B | 16 | C |
| 7 | C | 17 | D |
| 8 | D | 18 | C |
| 9 | D | 19 | C |
| 10 | C | 20 | B |
How Did You Score?
| Correct Answers | Performance |
|---|---|
| 18–20 | Excellent — You have a strong understanding of averages. |
| 15–17 | Very Good — Your fundamentals are clear; practice combined and replacement averages. |
| 11–14 | Good — Review missing-value and group-average problems. |
| 6–10 | Needs Practice — Revise the relationship between average, total, and number of observations. |
| 0–5 | Beginner — Begin with basic arithmetic mean questions and gradually move to applications. |
Important Average Formulas
Basic Average
[
\text{Average}
\frac{\text{Sum of Observations}}
{\text{Number of Observations}}
]
Finding the Total
If the average and number of observations are known:
[
\text{Total}
\text{Average}\times\text{Number of Observations}
]
For example:
Average = 25
Number of observations = 8
Therefore:
[
\text{Total}=25\times8=200
]
Finding a Missing Value
Suppose the average of 5 numbers is 30.
Their total must be:
[
5\times30=150
]
If four numbers total 112, the missing number is:
[
150-112=38
]
Average After Adding a New Observation
First calculate the original total:
[
\text{Original Average}\times\text{Original Number of Observations}
]
Add the new observation.
Then divide by the new number of observations.
Average After Removing an Observation
Calculate the original total.
Subtract the removed observation.
Then divide by the remaining number of observations.
Replacement Problems
Suppose the average of 10 people increases by 3 when one person is replaced.
The total increase is:
[
10\times3=30
]
Therefore, the incoming person’s value must be 30 greater than the outgoing person’s value.
This shortcut is particularly useful in age, salary, weight, and score questions.
Combined Average
A common mistake is to take the simple average of two averages without considering the size of each group.
Suppose:
20 students have an average score of 60.
30 students have an average score of 70.
The combined average is not necessarily 65.
Calculate the totals:
[
20\times60=1200
]
and:
[
30\times70=2100
]
Combined total:
[
1200+2100=3300
]
Total students:
[
20+30=50
]
Combined average:
[
\frac{3300}{50}=66
]
Therefore:
Combined Average = 66
Effect of Changing Every Observation
If the same number is added to every observation, the average increases by that number.
For example, if the average is:
30
and 5 is added to every observation, the new average becomes:
Similarly, if 4 is subtracted from every observation, the average decreases by 4.
If every observation is multiplied by 2, the average is also multiplied by 2.
Average of Consecutive Numbers
For an odd number of equally spaced consecutive values, the middle value is the average.
For example:
[
21,\ 23,\ 25,\ 27,\ 29
]
The average is:
[
25
]
which is the middle value.
This shortcut can save considerable time in aptitude tests.
Common Mistakes in Average Questions
Forgetting that average depends on group size
An average of 60 for 10 people and an average of 80 for 20 people cannot simply be averaged as:
[
\frac{60+80}{2}
]
because the group sizes are different.
Forgetting to correct the total
If a value was entered incorrectly, first adjust the total, then calculate the new average.
Confusing total increase with average increase
If the average of 8 people increases by 3, the total increases by:
[
8\times3=24
]
not simply 3.
Double-counting an overlapping observation
In questions involving the first (n) and last (n) observations, check whether one observation belongs to both groups.
Topics Covered in This Test
This Average aptitude test covered:
- Basic arithmetic mean
- Finding totals
- Marks and scores
- Adding observations
- Removing observations
- Consecutive numbers
- Required scores
- Salaries
- Incorrect observations
- Ages
- Combined averages
- Temperatures
- Changing every observation
- Replacement problems
- Weighted group averages
- Overlapping groups
Average concepts are also useful in Data Interpretation, Statistics, Ages, Mixtures, and placement aptitude tests.
Frequently Asked Questions
What is an average?
An average represents a central value obtained by dividing the total of all observations by the number of observations.
What is the formula for average?
[
\text{Average}
\frac{\text{Sum of Observations}}
{\text{Number of Observations}}
]
How can I find the total if the average is known?
Multiply the average by the number of observations.
For example:
Average = 18
Number of values = 7
Therefore:
[
18\times7=126
]
How do I solve average age questions?
Convert the average age into a total age first. Then add or subtract the age of the person entering or leaving the group and calculate the new average.
Can two averages simply be averaged?
Only when the two groups contain the same number of observations.
If the group sizes differ, calculate their totals and then determine the combined average.
What happens to the average if every value increases by 5?
The average also increases by 5.
Are Average questions important for placement tests?
Yes. Average questions are commonly included in quantitative aptitude assessments and are closely related to marks, ages, salaries, production, expenditure, and data interpretation.
What should I learn before attempting difficult Average questions?
Be comfortable with:
- basic arithmetic,
- fractions,
- percentages,
- ratios, and
- converting an average into a total.
Conclusion
Average questions become much easier when you stop treating the average as an isolated number and instead think in terms of:
Average × Number of Observations = Total
Most advanced average problems are simply variations of this relationship.
For questions involving a person joining, leaving, or being replaced, first determine how the total changes. For combined groups, always consider the number of observations in each group.
With regular practice, even complicated-looking average problems can often be reduced to a few simple calculations.
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