Simplification is the single most reliable scoring topic in IBPS RRB Office Assistant. The questions are not tricky — they test whether you process operations in the correct order and whether your mental arithmetic is fast enough under timed conditions. If you are dropping marks here, you are losing free points.
Here is the core idea: any arithmetic expression, no matter how tangled it looks, becomes trivial once you have a fixed processing order. That fixed order is BODMAS — Brackets, Orders (powers and roots), Division, Multiplication, Addition, Subtraction. Think of it as a traffic signal. No matter how many vehicles (operations) are waiting, they move only when their signal turns green, and the signal order never changes.
A useful analogy for the classroom: imagine you are a bank teller processing a transaction slip. The slip has instructions in a particular sequence — you do not process the last instruction first just because it is easier. The rules exist to ensure everyone arrives at the same final figure. BODMAS is that instruction sequence.
In IBPS RRB Clerk, simplification questions typically involve:
+, -, ×, ÷, powers, and bracketsThe expressions are kept moderate in complexity — no infinite nested brackets, no irrational numbers. The exam rewards candidates who have automatic recall of squares up to 25, cubes up to 12, and percentage-to-fraction conversions for common values. Build those as background infrastructure, and simplification becomes a 30-second topic per question.
BODMAS is an acronym for the order in which operations are evaluated:
| Letter | Operation | Priority |
|--------|-----------|----------|
| B | Brackets — resolve innermost first | 1st |
| O | Orders — powers (², ³) and roots (√) | 2nd |
| D | Division (÷) | 3rd (left to right) |
| M | Multiplication (×) | 3rd (left to right) |
| A | Addition (+) | 4th (left to right) |
| S | Subtraction (−) | 4th (left to right) |
Two critical clarifications that trip up candidates:
D and M have equal priority. When both appear in the same expression with no brackets separating them, you work left to right. So 84 ÷ 7 × 3 is (84 ÷ 7) × 3 = 12 × 3 = 36, not 84 ÷ (7 × 3) = 4. This is the most common error in RRB simplification questions.
A and S have equal priority. Similarly, 56 + 54 - 20 is processed left to right: (56 + 54) - 20 = 110 - 20 = 90. You will never go wrong if you always sweep left to right within the same priority tier.
Before you touch any +, -, ×, or ÷, compute all powers.
3² = 9, 4² = 16, 2³ = 8 — these should be instant recall, not calculations.
Build this table in your head:
1² = 1, 2² = 4, 3² = 9, 4² = 16, 5² = 25, 6² = 36, 7² = 49, 8² = 64, 9² = 81, 10² = 100, 11² = 121, 12² = 144, 13² = 169, 14² = 196, 15² = 2251³ = 1, 2³ = 8, 3³ = 27, 4³ = 64, 5³ = 125, 6³ = 216, 7³ = 343, 8³ = 512, 9³ = 729, 10³ = 1000In a question like 2⁴ + 3³ - 5², the "calculation" is actually just a lookup: 16 + 27 - 25. The arithmetic after that takes five seconds.
Percentage questions in simplification are almost always of the form:
(x% of A) + (y% of B) - (z% of C)
The fastest approach: convert each percentage to a fraction or a multiplier you already know.
Common conversions (memorise these as pairs):
10% = 1/10 — divide by 1020% = 1/5 — divide by 525% = 1/4 — divide by 450% = 1/2 — divide by 275% = 3/4 — three-quarters40% = 2/530% = 3/10So 75% of 240: you know 75% = 3/4, so (3/4) × 240 = 3 × 60 = 180. No long multiplication needed.
For 30% of 150: 30% = 3/10, so (3/10) × 150 = 3 × 15 = 45.
The moment you see a percentage value in this list, switch to the fraction form. It cuts multiplication effort by half.
When you have nested brackets, always work from the innermost outward:
( ) innermost[ ]{ }If all brackets are of the same type, start from the innermost nested one. Resolve it completely, then move outward. Never try to "flatten" the whole expression in one pass — that is where errors creep in.
For a complex expression like 15 + 8 × 3 - 12 ÷ 4, use three passes:
Pass 1 — Mark the orders: Identify and compute any powers or roots.
Pass 2 — Mark the D/M pairs: Underline every ÷ and × and compute them: 8 × 3 = 24, 12 ÷ 4 = 3. Rewrite the expression: 15 + 24 - 3.
Pass 3 — Left-to-right A/S: 15 + 24 = 39, 39 - 3 = 36.
This three-pass method is slower to describe than to execute. In practice, once it becomes habit, you do it in one visual sweep of the expression.
When you see a messy expression, mentally colour-code it before touching numbers: Red = brackets/powers (stop and compute first), Yellow = × and ÷ (compute next), Green = + and − (compute last). This visual separation prevents the most common error — accidentally adding before multiplying. Standard approach (reading left to right carelessly): 2-3 errors per mock. Colour-code approach: near-zero errors once the habit is set. The step count drops because you eliminate backtracking.
When you see any percentage from this set — 10%, 12.5%, 20%, 25%, 33.33%, 40%, 50%, 60%, 66.67%, 75%, 80% — never multiply by the decimal. Instead, flip to the fraction: 75% → 3/4, 40% → 2/5, 25% → 1/4. Example: 75% of 240 via decimal = 0.75 × 240 (awkward). Via fraction = (3/4) × 240 = 3 × 60 = 180. Time: decimal method ~20s, fraction flip ~6s. For a question with three percentage terms, this saves roughly 40 seconds total.
When you see a ÷ b × c, the automatic instinct is sometimes to compute b × c first (wrong). Lock in the rule: D and M are processed strictly left to right, no exceptions. Mnemonic: "Division gets the door" — when D appears before M reading left to right, it goes first. For 84 ÷ 7 × 3: left-to-right gives 12 × 3 = 36. The trap answer (doing 7 × 3 first) gives 84 ÷ 21 = 4. The correct answer is 4.5× larger — wrong answer, wrong option, zero marks. Recognizing this saves you from a wrong-answer trap in about 1 in 4 simplification questions.
Before you touch addition or subtraction in a power expression, write down all power values first as a separate step. For 2⁴ + 3³ - 5²: write 16 + 27 - 25 on your rough sheet, then compute. If you try to hold the original expression in your head while computing, you risk confusing 3³ with 3². The extra 3 seconds spent writing the expanded form saves the 30 seconds you lose when you have to recheck a wrong answer. Standard approach (mental only): ~4 errors per 10 such questions. Write-first approach: ~0-1 errors.
In IBPS RRB simplification, wrong options are usually far from the correct answer — often differing by 10-30%. Before computing, scan the options. If they are spread widely (e.g., 17, 42, 85, 130), a rough estimate rules out 2-3 options immediately, and you only need to verify one. For 84 ÷ 7 × 3 + 45 ÷ 5 × 2: rough estimate is 12 × 3 + 9 × 2 ≈ 36 + 18 = 54. If you got 54 in your head before formal calculation, you have already identified the answer without full working. Used on suitable questions, this cuts solving time from ~45s to ~15s.
When you open a simplification question in the exam hall, run this decision sequence:
Step 1 — Brackets present? Yes → resolve innermost bracket first, completely, then move outward. No → go to Step 2.
Step 2 — Powers or roots present? Yes → compute all of them immediately and rewrite the expression with their numeric values. No → go to Step 3.
Step 3 — Division or Multiplication present? Yes → scan left to right, compute each ÷ and × in order, rewrite. No → go to Step 4.
Step 4 — Addition and Subtraction only remaining? Yes → compute left to right. Done.
For percentage expressions: Convert every percentage to its fraction equivalent first, then multiply. Never use the decimal unless the percentage is an odd value like 37% or 43%.
Time target: Pure BODMAS — under 35 seconds. Percentage simplification — under 45 seconds. Power expression — under 30 seconds (mostly lookup time).
If your answer does not match any option, do not rework the whole problem immediately. First, recheck only Step 2 (powers are the most common error source), then recheck Step 3 (D/M order).
Why this question: This is the most foundational power-expression type. It tests whether you compute powers before adding/subtracting.
Solving path: Identify three power terms. Compute each: 3² = 9, 4² = 16, 2³ = 8. Rewrite: 9 + 16 - 8. Left to right: 9 + 16 = 25, 25 - 8 = 17. Answer: 17.
Why this question: Classic D/M order trap. Many candidates do 7 × 3 first or 5 × 2 first — both are wrong.
Solving path: Two separate D/M chains separated by +. Chain 1: 84 ÷ 7 = 12, then 12 × 3 = 36. Chain 2: 45 ÷ 5 = 9, then 9 × 2 = 18. Addition: 36 + 18 = 54. Answer: 54.
Why this question: Percentage simplification — tests fraction-conversion speed for 75% and 30%.
Solving path: Convert percentages. 75% = 3/4, so (3/4) × 240 = 180. 30% = 3/10, so (3/10) × 150 = 45. Sum: 180 + 45 = 225. Answer: 225.
Why this question: Tests pure multiplication followed by A/S. All D/M operations must complete before any addition or subtraction.
Solving path: Three multiplication pairs first. 7 × 8 = 56, 9 × 6 = 54, 4 × 5 = 20. Rewrite: 56 + 54 - 20. Left to right: 56 + 54 = 110, 110 - 20 = 90. Answer: 90.
Why this question: Mixed expression with D, M, and A/S. The BODMAS three-pass method in action.
Solving path: Pass 2 (D/M): 8 × 3 = 24, 12 ÷ 4 = 3. Rewrite: 15 + 24 - 3. Pass 3 (A/S): 15 + 24 = 39, 39 - 3 = 36. Answer: 36.
Processing D/M right to left. In 84 ÷ 7 × 3, computing 7 × 3 = 21 first gives 84 ÷ 21 = 4 — completely wrong. Division and multiplication are processed strictly left to right. Lock this in before anything else.
Skipping the power step. In expressions like 2⁴ + 3³ - 5², candidates sometimes compute 2 + 3 - 5 first (the bases) and then deal with the powers, arriving at bizarre results. Powers come second in BODMAS, before all four arithmetic operations.
Using decimal multiplication for common percentages. Computing 0.75 × 240 longhand wastes 15-20 seconds per term. The fraction method (3/4 × 240) is faster and less error-prone for every percentage with a clean fraction equivalent.
Treating brackets as suggestions. Any expression inside brackets must be fully resolved before it interacts with anything outside, even if the operation outside seems "simpler" or "higher priority." Brackets override all other rules.
Adding before multiplying in mixed expressions. In 15 + 8 × 3 - 12 ÷ 4, the temptation is to do 15 + 8 = 23 first because addition appears first reading left to right. This is wrong. Multiplication and division always outrank addition and subtraction regardless of position.
Mental arithmetic errors on cubes. 3³ is 27, not 9. 4³ is 64, not 16. Confusing cubes with squares happens under time pressure. Writing the expanded values on your rough sheet before computing the final arithmetic eliminates this entirely.