Practice Questions
Concept Explanation
The average (arithmetic mean) of n numbers is their sum divided by n.
Average = Sum of all values / Number of values
Key Formulas
- Sum = Average × Number of values
- Missing value = (Average × n) − Sum of known values
- If each value increases by k, the average also increases by k.
Placement Shortcut
First find total sum from the average, then subtract known values to get the missing number.
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Q1 Easy
What is the average of 12, 18, 24 and 30?
ExplanationSum = 84. Average = 84/4 = 21. -
Q2 Easy
The average of 6 numbers is 15. What is their sum?
ExplanationSum = 15 × 6 = 90. -
Q3 Medium
Average of 8 numbers is 25. If 32 is excluded, the sum of the remaining 7 numbers is:
ExplanationTotal sum = 200. Remaining sum = 200 − 32 = 168. -
Q4 Easy
Five numbers have average 18. Four of them are 15, 17, 19 and 21. Find the fifth.
ExplanationTotal = 90. Fifth = 90 − 72 = 18. -
Q5 Easy
Average of first 10 natural numbers is:
ExplanationSum = 55. Average = 55/10 = 5.5. -
Q6 Medium
The average of 3, 7, 11, 15 and x is 9. Find x.
ExplanationTotal = 45. Sum of known = 36. x = 9. -
Q7 Easy
Average of 20 numbers is 35. If each number is increased by 5, the new average is:
ExplanationIncreasing each value by 5 increases the average by 5 → 40.
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Q8 Medium
Average of 4 numbers is 27.5. Three numbers are 25, 28 and 30. The fourth is:
ExplanationTotal = 110. Fourth = 110 − 83 = 27. -
Q9 Hard
Average of 9 numbers is 50. Average of first 5 is 45 and of last 5 is 55. Find the middle number.
ExplanationTotal = 450. First 5 = 225, last 5 = 275. Middle = 225 + 275 − 450 = 50. -
Q10 Medium
Average of 7 consecutive even numbers is 26. The largest number is:
ExplanationMiddle term = 26. Set: 20, 22, 24, 26, 28, 30, 32. -
Q11 Hard
The average of 15 numbers is 40. One number 55 is replaced by 25. The new average is:
ExplanationSum decreases by 30. New average = 40 − 30/15 = 38. -
Q12 Easy
The average of 16, 20, 24, 28 and n is 22. Find n.
ExplanationTotal = 110. Known sum = 88. n = 22. -
Q13 Hard
Average of 5 observations is 32. Average of first 3 is 26 and of last 3 is 34. Find the third observation.
ExplanationTotal = 160. First 3 sum = 78, last 3 sum = 102. Third = 78 + 102 − 160 = 20. -
Q14 Medium
Average of 5 numbers is 12. If 20 is removed, the average of the remaining 4 is:
ExplanationTotal = 60. Remaining sum = 40. Average = 40/4 = 10.
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DS1 Easy
What is the average of the numbers?
Statement IThe numbers are 14, 22, 18 and 26.
Statement IIThe sum of the numbers is 80 and there are 4 numbers.
ExplanationEach statement alone gives average = 80/4 = 20. -
DS2 Medium
What is the missing number?
Statement IThe average of 5 numbers is 30.
Statement IIFour numbers are 25, 28, 32 and 35.
ExplanationTogether: total = 150, known sum = 120, missing = 30.
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DS3 Easy
What is the average of the set?
Statement IThere are 6 numbers in the set.
Statement IIThe sum of the numbers is 144.
ExplanationNeed both count and sum. Average = 144/6 = 24. -
DS4 Medium
Is the average greater than 50?
Statement IThe sum of 8 numbers is 400.
Statement IIThe smallest number in the set is 45.
ExplanationStatement I: average = 50, so it is not greater than 50.