SBI Clerk · Bite-size lessons

Simplification and Approximation

About 6 min · Numerical Ability · English

Time worked out from the lesson's 337 words at 150 words a minute, plus a minute for each question.

Simplification and Approximation is a topic in SBI Clerk Prelims Numerical Ability section. These questions reward speed over complexity—most involve basic arithmetic but under strict time pressure (about 20 minutes for 35 questions).

Key ideas

• BODMAS Rule: Brackets → Orders (powers, roots) → Division → Multiplication → Addition → Subtraction. Division and multiplication have equal priority, as do addition and subtraction; within each pair, work left to right.
• Approximation Threshold: When a question says "approximate value" or "≈", round numbers to nearest convenient values before calculating. Typically round to nearest 5, 10, or whole number.
• Percentage-Decimal-Fraction Equivalence: Instantly convert between forms. For example, 12.5% = 1/8 = 0.125. This speeds up mixed calculations.
• Square and Cube Recognition: Identify perfect squares (1 to 30) and cubes (1 to 15) on sight. Many expressions contain hidden squares/cubes.
• Fraction Simplification: Always reduce fractions before multiplying. Cancel common factors across numerator and denominator early.

Watch out for

• Ignoring BODMAS in left-to-right sequences → Students compute 20 – 5 + 3 as 20 – 8 = 12 instead of correct (20 – 5) + 3 = 18. Addition and subtraction are equal priority; work left to right.
• Over-approximating in close-option questions → Rounding 7.89 to 8 and 51.2 to 50 when options differ by only 10 causes wrong picks. Check option spread first; tighten estimates for close options.
• Forgetting "of" means multiplication → Reading "25% of 60% of 400" and adding instead of multiplying. Compute as 0.25 × 0.6 × 400 = 60.

Quick reference

• BODMAS: Brackets → Orders → Division → Multiplication → Addition → Subtraction
• For approximation: round to nearest 5 or 10, then compute
• "Of" = × (multiplication)
• Know squares 1–30 and cubes 1–15 cold
• Check option gaps before deciding how roughly to estimate

Check yourself: 3 questions

This lesson is cut from the topic's note, not rewritten. Fact-checked on 18 Oct 2026: an AI-assisted check of this note against cited sources; the errors it found were corrected that day. Some errors may remain. The questions are from Shishya's validated question bank.

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