IBPS Clerk · Bite-size lessons
Arithmetic
About 6 min · Numerical Ability · English
Time worked out from the lesson's 362 words at 150 words a minute, plus a minute for each question.
These questions test your ability to apply fundamental mathematical concepts to real-world scenarios—calculating interest, splitting profits, finding ages, or measuring speeds.
Key ideas
- Percentage is the foundation: Almost every arithmetic topic—profit/loss, interest, partnership—uses percentage calculations. Master fraction-to-percentage conversions first.
- Ratio links quantities: Ratios compare two quantities; proportions state that two ratios are equal. Always reduce ratios to simplest form before solving.
- Average = Sum ÷ Count: The weighted average formula is essential when groups have different sizes.
- Profit/Loss is always on Cost Price: Unless stated otherwise, profit% and loss% are calculated on CP, not SP.
- Interest problems differentiate SI and CI: SI grows linearly; CI grows exponentially. For 2-year problems, CI – SI = P × (R/100)².
Watch out for
- Calculating profit% on SP instead of CP → Always use CP as the base unless the question explicitly says otherwise.
- Confusing SI and CI formulas for 2+ years → SI uses simple multiplication (P×R×T/100); CI requires the power formula. Don't interchange.
- Forgetting to convert units → Speed in km/hr and time in minutes will give wrong answers. Convert to consistent units first.
Quick reference
- Successive % change: a + b + ab/100 — memorize this for two consecutive changes.
- 1/6 = 16.67%, 1/7 ≈ 14.28%, 1/8 = 12.5% — learn fraction-percentage pairs up to 1/15.
- CI – SI for 2 years = P × (R/100)² — instant formula, no derivation needed.
- Average speed for equal distances = 2S1S2 / (S1 + S2) — not the simple average.
- LCM method beats equation method in Time & Work — always assign total work = LCM of days.
Check yourself: 3 questions
1. A shopkeeper marks an article 30% above its cost price and then allows a discount of 15%. If the cost price of the article is Rs. 800, what is his profit percentage?
2. A sum of money amounts to Rs. 13,380 in 2 years and to Rs. 14,910 in 3 years at simple interest. What is the rate of interest per annum?
3. A train crosses a platform 240 meters long in 30 seconds and crosses a pole in 18 seconds. What is the speed of the train in km/hr?
This lesson is cut from the topic's note, not rewritten. Fact-checked on 17 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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