Average
Average
Average equals Sum divided by Count. Exams twist this with member additions, removals, replacements, and group merges. Banking and SSC papers carry 2\u20133 average questions per paper, and the replacement variant appears most frequently.
Key Idea
Work backwards from Average: Sum = Average × Count. This single formula solves 80% of average problems.
Core Formulas
Average
Average = Sum / Count → Sum = Average × Count
Start every average problem here \u2014 compute the total sum first, then manipulate it based on the condition given.
Weighted Average
Combined Avg = (n₁×a₁ + n₂×a₂) / (n₁ + n₂)
Merge two groups of different sizes into one and compute the combined average directly.
Effect of Adding a New Term
New term = New Avg × (n+1) − Old Avg × n
When the average changes after one more element is included.
Effect of Replacing a Term
Change in average = (New value − Old value) / n
When one member leaves and another joins — find how much the average shifts.
Average of Consecutive Integers
Avg = (First + Last) / 2 = middle term
For any evenly-spaced sequence; the average equals the middle value.
Relevant Exams
Average questions appear in virtually every banking and SSC exam — replacement and weighted-average variants are the most tested sub-types.