The real challenge is speed
Prelims Numerical Ability has 35 questions in 20 minutes. Mains Quantitative Aptitude has 50 questions in 45 minutes. Calculators are not allowed. SBI's booklet says the test measures "how fast and accurate you are in dealing with numbers, viz. computation, quantitative reasoning, interpretation of tables and graphs".
The maths itself is mostly Class 8 to 10 level. What separates scores is calculation speed and the judgement to skip long questions.
Numbers to know by heart
- Tables up to 20 and squares up to 30 (for example 17² = 289, 23² = 529, 27² = 729).
- Cubes up to 20 (for example 13³ = 2197, 17³ = 4913).
- Fractions as percentages:
| Fraction | Percent | Fraction | Percent |
|---|---|---|---|
| 1/2 | 50% | 1/9 | 11.11% |
| 1/3 | 33.33% | 1/11 | 9.09% |
| 1/6 | 16.67% | 1/12 | 8.33% |
| 1/7 | 14.29% | 1/16 | 6.25% |
| 1/8 | 12.5% | 1/20 | 5% |
Calculation speed tricks
Squares of numbers ending in 5
Multiply the tens digit by the next number and write 25 after it. 65 x 65: 6 x 7 = 42, so the answer is 4225. 85 x 85: 8 x 9 = 72, so 7225.
Multiplying a two-digit number by 11
Write the two digits apart and put their sum in the middle. 43 x 11: 4, (4+3), 3 = 473. If the sum is 10 or more, carry: 78 x 11: 7, 15, 8 becomes 858.
Percentage swap
x% of y = y% of x. So 16% of 25 = 25% of 16 = 4. 18% of 50 = 50% of 18 = 9.
Successive percentage change
Two changes of a% and b% give a net change of a + b + ab/100. A 20% rise followed by a 10% fall: 20 - 10 + (20 x -10)/100 = 8% net rise.
Multiplying numbers near 100
97 x 96: both are below 100 by 3 and 4. Subtract crosswise, 97 - 4 = 93, and multiply the gaps, 3 x 4 = 12. Answer: 9312.
Unit digit check
Before choosing an option in simplification, check the last digit. 347 x 26 must end in 2 (7 x 6 = 42). Often only one option survives.
Simplification and approximation
These are the fastest marks in Prelims. Follow BODMAS strictly and simplify fractions before multiplying.
For approximation, round each number to a friendly value and check how far apart the options are. Example: 39.89% of 650.12 + 14.9 x 6.02 is roughly 40% of 650 + 15 x 6 = 260 + 90 = 350. If the options are 310, 350, 390, 420 and 450, the answer is clearly 350.
Arithmetic word problems
| Topic | Method that saves time |
|---|---|
| Percentage, profit and loss | Work in fractions. A 25% profit means SP = 5/4 of CP. A discount of 20% means pay 4/5. |
| Ratio and partnership | Profit is shared in the ratio of capital x time. |
| Time and work, pipes | Use the LCM of days as total work. If A takes 12 days and B takes 18, total work = 36 units, A does 3 a day, B does 2, together 5, so 36/5 = 7.2 days. |
| Speed, distance, time | For equal distances at speeds a and b, average speed = 2ab/(a+b). At 40 and 60 km/h, that is 48 km/h, not 50. |
| Boats and streams | Downstream = boat + stream; upstream = boat - stream. |
| Simple and compound interest | For 2 years, CI - SI = P(r/100)². At 10% on ₹5,000, the difference is ₹50. |
| Mixtures and alligation | Use the alligation cross to find the ratio of mixing. |
| Mensuration | Memorise volume and surface formulas of cylinder, cone and sphere. |
DI, number series and quadratic equations
Data interpretation
- Read titles, units and totals before reading questions.
- Compare using ratios rather than exact division. To ask whether 347/512 is bigger than 2/3, check 3 x 347 = 1041 against 2 x 512 = 1024. It is bigger.
- For percentage change, estimate first: from 480 to 540 is a rise of 60, which is 12.5% of 480.
Number series
Check in this order: differences, second differences, multiplication patterns (x2 +1, x3 -2), squares and cubes, alternating series. Example: 3, 7, 15, 31, 63, ? follows x2 +1, so the next term is 127.
Quadratic equations
Factorise both equations and compare roots. For x² - 7x + 12 = 0, roots are 3 and 4. For y² - 9y + 20 = 0, roots are 4 and 5. Every x is less than or equal to every y, so x ≤ y.
How to practise Quant
- Learn one topic's method, then do 30 to 40 questions on it in one sitting, timed.
- Do a 10-minute speed drill of 20 simplification or approximation questions every day.
- Do at least one DI set daily from the second month onward.
- In mocks, skip any question you cannot start within 15 seconds. Come back if time permits.
Skipping smartly
In a 20-minute Quant section, the questions you skip matter as much as the ones you solve. Skip on sight if a question:
- needs more than two lines of setup before any calculation;
- has ugly numbers in a DI set while another set has round numbers;
- is from a low-priority topic you have not practised, such as probability.
Mark it and return only if time remains. Thirty seconds saved on each of three hard questions buys you two easy ones elsewhere.
Questions about this
Is a calculator allowed in SBI Clerk?
No. The notification says candidates are not permitted to use or possess calculators in the examination premises.
Which Quant topics are most important for Prelims?
Simplification, approximation, arithmetic word problems and data interpretation have carried the most questions in recent papers, followed by number series and quadratic equations.
How can I increase my calculation speed?
Memorise squares to 30, cubes to 20 and the fraction-percentage table, then do a 10-minute daily speed drill. Tricks only help after the basic numbers are automatic.