Practice Questions
Concept Explanation
Average-based DI uses mean values from grouped data, monthly totals, or weighted combinations.
Key Formulas
- Simple average = sum ÷ count.
- Weighted average = Σ(value × weight) ÷ Σweights.
- If average of n numbers is A and one number x is added: new average = (nA + x)/(n + 1).
Example
Scores 60, 80, 100: average = 240/3 = 80.
Common Trap
Average of averages is wrong unless groups have equal size.
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Q1 Easy
Monthly sales: 80, 100, 120 (Rs. lakh). Average monthly sales is:
Explanation(80+100+120)/3 = 100. -
Q2 Easy
Five days production: 50, 60, 70, 80, 90 units. Average is:
Explanation350/5 = 70. -
Q3 Easy
Average of 40, 60, 80, 100 is:
Explanation280/4 = 70. -
Q4 Medium
Class A average = 70 (30 students), Class B average = 80 (20 students). Combined average is:
ExplanationTotal marks = 2100 + 1600 = 3700. Combined average = 3700/50 = 74. -
Q5 Easy
Average of 5 numbers is 48. Their total is:
Explanation48 × 5 = 240. -
Q6 Easy
Runs in 4 innings: 40, 50, 60, 70. Average runs per inning is:
Explanation220/4 = 55. -
Q7 Medium
10 items at Rs. 20 and 20 items at Rs. 35. Average price per item is:
ExplanationTotal = 200 + 700 = 900 for 30 items. Average = 30.
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Q8 Easy
Average of first 10 numbers is 15. Sum of first 10 numbers is:
Explanation15 × 10 = 150. -
Q9 Easy
Three months average temperature 28°C, 32°C, 30°C. Overall average is:
Explanation(28+32+30)/3 = 30°C. -
Q10 Hard
Average of 6 numbers is 25. If one number 40 is replaced by 10, new average is:
ExplanationOld sum = 150. New sum = 150 − 40 + 10 = 120. New average = 120/6 = 20. -
Q11 Hard
Quarterly revenue average Rs. 120 lakh; Q1, Q2, Q3 are 100, 110, 130. Q4 revenue is:
ExplanationTotal for 4 quarters = 480. Q4 = 480 − 340 = 140. -
Q12 Medium
Average daily sales Mon–Fri: 72, 78, 84, 90, 96. Weekly average (5 days) is:
Explanation420/5 = 84. -
Q13 Medium
Group of 4 averages 50; a fifth value 70 is added. New average is:
ExplanationOld sum = 200. New sum = 270. Average = 270/5 = 54. -
Q14 Hard
Weighted: 5 workers avg 8 hrs, 3 workers avg 10 hrs. Overall average hours is:
Explanation(40+30)/8 = 70/8 = 8.75 hrs.
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DS1 Easy
What is the average of 80, 100 and 120?
Statement IThe three values are 80, 100, 120.
Statement IITheir sum is 300.
ExplanationStatement I alone: average = 100. -
DS2 Medium
What is the combined average of two classes?
Statement IClass A: 30 students, average 70.
Statement IIClass B: 20 students, average 80.
ExplanationNeed both class sizes and averages: combined = 74.
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DS3 Hard
What is Q4 revenue if quarterly average is Rs. 120 lakh?
Statement IQ1 = 100, Q2 = 110, Q3 = 130.
Statement IIAverage of four quarters is Rs. 120 lakh.
ExplanationNeed both Q1–Q3 and the average to find Q4 = 140. -
DS4 Hard
What is the new average after replacing 40 by 10 in six numbers averaging 25?
Statement IOriginal average of 6 numbers is 25.
Statement II40 is replaced by 10.
ExplanationNeed both facts: new average = 20.