Average and speed problems together contribute 4–7 questions to SBI PO Prelims Quantitative Aptitude — across standalone questions and as embedded components of data interpretation sets. Students who apply the standard sum-and-divide method for averages and the distance-equals-speed-times-time formula for every speed question consistently run out of time.
The shortcuts in this guide don't just save seconds — they eliminate entire calculation steps. Once you internalise the deviation method for averages and the harmonic mean approach for speed, most questions become two-step solves.
- Average and speed questions contribute 4–7 marks in SBI PO Prelims across Quant and DI
- The deviation method finds averages by working with differences from an assumed mean — faster for large numbers
- Harmonic mean (2ab/a+b) is the correct formula for average speed when distance is equal — not arithmetic mean
- Relative speed = sum of speeds (opposite direction) or difference of speeds (same direction)
- Ten days of shortcut-based daily practice (15 questions/day) achieves full accuracy on both topics
Source: SBI PO 2024 official exam pattern — sbi.co.in
Average Shortcuts: The Deviation Method
The standard average formula — sum all values, divide by count — is reliable but slow when numbers are large or irregular. The deviation method is 2–3x faster for most SBI PO average questions.
How the deviation method works:
- Choose an assumed mean (AM) — pick any convenient number close to the middle of the data
- Find the deviation of each value from AM (value − AM)
- Find the average of the deviations
- True average = AM + average deviation
Find the average of 87, 92, 78, 95, 83. Assumed mean = 87. Deviations: 0, +5, −9, +8, −4. Sum = 0. Average deviation = 0. True average = 87. Done in under 10 seconds.
Karthik from Chennai cleared SBI PO 2024 after switching to this method: "I used to add all numbers manually for average questions. The deviation method cut my calculation time from 45 seconds to 12 seconds on every average question."
The Missing Value Shortcut
When a set's average is given and one value is missing, use: Missing value = (Target average × New count) − Sum of known values. This is faster than back-calculating from the standard formula.
Speed Shortcuts: The 3 Methods That Cover Everything
Shortcut 1: Harmonic Mean for Equal Distance
The most common SBI PO speed error is applying arithmetic mean when a journey has two legs of equal distance at different speeds. The correct formula is harmonic mean:
Average speed = 2ab / (a + b)
Where a and b are the two speeds. Arithmetic mean always gives a higher (wrong) answer — using it costs you the mark.
Shortcut 2: Relative Speed
- Opposite directions: Relative speed = Speed A + Speed B
- Same direction: Relative speed = Speed A − Speed B (larger minus smaller)
This applies directly to train-crossing questions, meeting-point problems, and catch-up scenarios. Identify direction first, apply the correct formula, then use Time = Distance / Relative Speed.
Shortcut 3: Time-Speed Inverse Relationship
When distance is constant, time and speed are inversely proportional. If speed increases by a ratio of m:n, time decreases by n:m. This eliminates calculation entirely for ratio-based speed questions.
SBI PO Average and Speed Question Types: Quick Reference
| Question Type | Shortcut | Time Target |
|---|---|---|
| Simple average | Deviation method | 12 seconds |
| Missing value in average | Target × n − known sum | 15 seconds |
| Average speed, equal distance | Harmonic mean 2ab/(a+b) | 15 seconds |
| Average speed, equal time | Arithmetic mean (a+b)/2 | 10 seconds |
| Train crossing / meeting | Relative speed method | 20 seconds |
| Time-speed ratio change | Inverse proportion | 10 seconds |
Source: SBI PO 2022–2024 paper analysis, bankersadda.com
Your 10-Day Action Plan
Days 1–4: Average Drilling — Practise average questions using only the deviation method (15/day). Use the missing value shortcut for every missing-member question. Avoid the sum-and-divide approach entirely during this phase to force the new habit.
Days 5–8: Speed Shortcuts — Drill speed questions by type — equal distance (harmonic mean), equal time (arithmetic mean), and relative speed separately. Target: identifying the correct method within 5 seconds of reading the question.
Days 9–10: Mixed Timed Practice — Combine average and speed questions (20/day) under SBI PO Prelims timing. Any question exceeding 30 seconds needs method revision, not more calculation practice.
In our analysis of 500+ PrepGrind students, those who switched from standard formula application to the deviation method and harmonic mean approach improved combined average-speed accuracy from 61% to 89% within ten days (PrepGrind internal data, 2024).
People Also Search For
How to score 70 marks in SBI PO exam?
To score around 70 marks, candidates should focus on high-accuracy attempts and effective time management. Regular mock test practice and quick revision of important arithmetic formulas help in improving performance. Strong basics in reasoning and English comprehension are also essential. Analysing mistakes after each test boosts overall score.
Is 60% necessary for SBI PO eligibility?
Eligibility for SBI PO mainly requires a graduation degree from a recognised university, and percentage criteria may vary as per the official notification. Some recruitments may not require a fixed percentage for certain categories. Candidates should check the latest guidelines before applying. Proper awareness helps avoid application rejection.
How to solve simplification questions faster in bank exams?
Candidates should learn calculation shortcuts like BODMAS rule application, square and cube values, and approximation methods. Improving mental maths speed helps in solving simplification questions quickly. Regular practice of mock tests increases accuracy and confidence. Avoid lengthy calculations by using smart techniques.
What are important speed maths topics for bank exams?
Important topics include percentage, ratio and proportion, simplification, approximation, averages, profit and loss, time and work, and data interpretation. Candidates should focus on concept clarity and regular revision. Sectional mock tests help in identifying weak areas. Consistent practice improves overall quantitative aptitude score.
How to convert percentage to fraction quickly in exams?
Candidates can memorise common conversions like 50% = 1/2, 25% = 1/4, 20% = 1/5, and 12.5% = 1/8 for faster calculations. Using fraction conversion reduces time in arithmetic questions. Practising mixed problems improves speed and accuracy. Regular revision strengthens calculation confidence.
Conclusion: Your Next Step
SBI PO average and speed calculation shortcuts reduce every question to a fast, two-step solve. Use the deviation method for averages, always verify whether distance or time is equal before choosing your speed formula, and apply relative speed immediately for train and meeting problems. Ten days of deliberate shortcut practice makes all three habits automatic.
Ready to build complete SBI PO Quantitative Aptitude mastery? Explore PrepGrind's SBI PO Quant module — featuring 400+ average and speed drills across all question types, timed mock sets, and expert video solutions built by Bank PO toppers.