Average questions

Aptitude Updated 11 Oct 2026

These average questions cover everything asked on averages in SSC, bank, railway and campus placement aptitude tests. Each question has four options, the correct answer and a worked solution of one to three steps.

The page begins with basic average aptitude questions on sums and missing numbers, then moves to consecutive numbers and series, followed by replacement, wrong entry and combined average problems. The last section has exam and placement level questions on average speed, batting averages, income and temperatures. Every answer has been calculated, so you can use the solutions to check your own method.

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Basic average questions

Q1. What is the average of 12, 18, 25, 31 and 44?
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Answer: D. 26
Sum = 130, count = 5. Average = 130 ÷ 5 = 26.
Q2. What is the average of the first 10 natural numbers?
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Answer: C. 5.5
Sum of 1 to 10 = 10 x 11 ÷ 2 = 55. Average = 55 ÷ 10 = 5.5.
Q3. What is the average of the first 20 even numbers?
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Answer: D. 21
First 20 even numbers are 2 to 40. Average = (first + last) ÷ 2 = (2 + 40) ÷ 2 = 21.
Q4. What is the average of the first 15 odd numbers?
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Answer: C. 15
The first n odd numbers add up to n x n = 225. Average = 225 ÷ 15 = 15.
Q5. What is the average of the first 10 multiples of 7?
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Answer: A. 38.5
Multiples are 7 to 70. Average = (7 + 70) ÷ 2 = 38.5.
Q6. The average of 6 numbers is 45. What is their sum?
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Answer: D. 270
Sum = average x count = 45 x 6 = 270.
Q7. The average of five numbers is 30. Four of them are 24, 28, 35 and 31. What is the fifth number?
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Answer: C. 32
Total = 5 x 30 = 150. Sum of four = 118. Fifth = 150 - 118 = 32.
Q8. A student scores 72, 85, 64, 91 and 78 marks in five subjects. What are the average marks?
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Answer: D. 78
Total = 390. Average = 390 ÷ 5 = 78.
Q9. The average of four numbers is 20. If each number is multiplied by 3, what is the new average?
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Answer: A. 60
Multiplying every number by 3 multiplies the sum, and so the average, by 3: 20 x 3 = 60.

Average of consecutive numbers and series

Q10. The average of five consecutive numbers is 24. What is the largest of them?
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Answer: B. 26
For an odd count of consecutive numbers the average is the middle one, so the numbers are 22 to 26. Largest = 26.
Q11. The average of seven consecutive odd numbers is 33. What is the smallest of them?
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Answer: D. 27
The middle (4th) number is 33. The smallest is 3 steps of 2 below it: 33 - 6 = 27.
Q12. The average of four consecutive even numbers is 15. What is the largest number?
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Answer: B. 18
The numbers are 12, 14, 16, 18 (their average is (12 + 18) ÷ 2 = 15). Largest = 18.
Q13. What is the average of all natural numbers from 1 to 50?
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Answer: A. 25.5
Average of 1 to n = (n + 1) ÷ 2 = 51 ÷ 2 = 25.5.
Q14. What is the average of the squares of the first 10 natural numbers?
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Answer: D. 38.5
Sum = n(n + 1)(2n + 1) ÷ 6 = 10 x 11 x 21 ÷ 6 = 385. Average = 385 ÷ 10 = 38.5.
Q15. What is the average of the first 10 prime numbers?
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Answer: B. 12.9
Primes: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29. Sum = 129. Average = 129 ÷ 10 = 12.9.

Replacement, wrong entry and combined average questions

Q16. The average age of 30 students is 14 years. When the teacher's age is included, the average becomes 15 years. What is the teacher's age?
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Answer: D. 45
Teacher's age = 31 x 15 - 30 x 14 = 465 - 420 = 45 years.
Q17. The average weight of 8 people increases by 2.5 kg when a person weighing 65 kg is replaced by a new person. What is the weight of the new person?
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Answer: D. 85
Total increase = 8 x 2.5 = 20 kg. New person = 65 + 20 = 85 kg.
Q18. The average of 20 numbers was found to be 56. Later it was found that 64 had been wrongly read as 46. What is the correct average?
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Answer: B. 56.9
Correct sum = 20 x 56 - 46 + 64 = 1138. Correct average = 1138 ÷ 20 = 56.9.
Q19. The average of 11 results is 50. The average of the first six is 49 and that of the last six is 52. What is the sixth result?
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Answer: C. 56
The sixth result is counted twice: 6 x 49 + 6 x 52 - 11 x 50 = 294 + 312 - 550 = 56.
Q20. The average of 10 numbers is 40. When one number is removed, the average of the rest becomes 38. Which number was removed?
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Answer: D. 58
Removed number = 10 x 40 - 9 x 38 = 400 - 342 = 58.
Q21. The average weight of A, B and C is 45 kg. The average weight of A and B is 40 kg, and that of B and C is 43 kg. What is the weight of B?
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Answer: C. 31
A + B + C = 135, A + B = 80, B + C = 86. B = 80 + 86 - 135 = 31 kg.
Q22. Section A has 40 students with average marks 60, and section B has 60 students with average marks 70. What is the average of all 100 students?
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Answer: C. 66
Total = 40 x 60 + 60 x 70 = 6600. Average = 6600 ÷ 100 = 66.
Q23. At the time of their marriage, the average age of a husband and wife was 25 years. Six years later, they have a one-year-old child. What is the average age of the family of three?
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Answer: C. 21
Couple's total now = 2 x 25 + 2 x 6 = 62. Family total = 62 + 1 = 63. Average = 63 ÷ 3 = 21 years.

Exam and placement level average aptitude questions

Q24. A cyclist rides to a village at 12 km/h and returns by the same road at 18 km/h. What is the average speed for the round trip?
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Answer: B. 14.4
For equal distances, average speed = 2xy ÷ (x + y) = 2 x 12 x 18 ÷ 30 = 14.4 km/h.
Q25. A batsman has an average of 32 runs after 10 innings. How many runs must he score in the 11th innings to raise his average to 35?
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Answer: A. 65
Runs needed = 11 x 35 - 10 x 32 = 385 - 320 = 65.
Q26. A batsman scores 87 runs in his 17th innings and his average increases by 3. What is his average after the 17th innings?
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Answer: B. 39
Let the old average be x. 16x + 87 = 17(x + 3), so x = 87 - 51 = 36. New average = 36 + 3 = 39.
Q27. A man spends an average of 4,500 rupees a month for the first 3 months and 5,200 rupees a month for the next 9 months. He saves 8,700 rupees in the year. What is his average monthly income?
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Answer: C. 5750
Total spending = 13,500 + 46,800 = 60,300. Income = 60,300 + 8,700 = 69,000. Average = 69,000 ÷ 12 = 5750 rupees.
Q28. The average temperature from Monday to Wednesday was 37 °C and from Tuesday to Thursday was 34 °C. If Thursday's temperature was 4/5 of Monday's, what was Thursday's temperature?
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Answer: C. 36
Monday - Thursday = 3 x 37 - 3 x 34 = 9. With Thursday = 0.8 x Monday, 0.2 x Monday = 9, so Monday = 45 and Thursday = 36 °C.
Q29. Of three numbers, the first is twice the second and three times the third. If their average is 44, what is the largest number?
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Answer: D. 72
Let the first be x. Then x + x/2 + x/3 = 3 x 44 = 132, so 11x/6 = 132 and x = 72.
Q30. The average of five consecutive numbers is n. If the next two numbers are also included, by how much does the average increase?
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Answer: D. 1
Check with n = 10: numbers 8 to 12, adding 13 and 14 makes 8 to 14, whose average is 11. So the average rises by 1.

How to prepare

Every average question rests on one formula: average = sum ÷ count, or sum = average x count. Turn each statement into a total first, then add or subtract totals; this avoids most errors. For consecutive numbers or any arithmetic series, the average is simply (first + last) ÷ 2, and for an odd count it is the middle term.

For replacement questions, the change in total equals count x change in average, so new value = old value + count x increase. For a wrong entry, correct the total and divide again. For average speed over equal distances, use 2xy ÷ (x + y) and never the simple mean of the two speeds. When a question has a variable such as n, test it with a small number to confirm the answer.

Study tips

Convert every average in the question into a total before doing anything else.
For series and consecutive numbers, use (first + last) ÷ 2 instead of adding all the terms.
Memorise the equal-distance average speed formula 2xy ÷ (x + y), since it appears often in placement tests.

Questions people ask

What is the formula for average?

Average = sum of observations ÷ number of observations. Most average questions are solved by turning averages into totals with sum = average x count.

How do I solve average aptitude questions quickly?

Work with totals, use (first + last) ÷ 2 for series, and use the change-in-total method for replacement questions. These shortcuts let you solve most questions in under a minute.

Why is average speed not the simple mean of two speeds?

When equal distances are covered at different speeds, more time is spent at the lower speed. So the average speed is 2xy ÷ (x + y), which is always less than the simple mean of x and y.

Are averages questions asked in placement tests?

Yes, averages appear in almost every placement and government exam aptitude section. They also form the base for mixtures, alligation and data interpretation questions.

Every question on this page is written and fact-checked by the GK Quizzes team. Spotted a mistake? Tell us and we will fix it. How we make our questions.