Tools
Calculation speed drill
Nobody loses a quantitative section because they cannot divide. They lose it because each division costs eight seconds of conscious thought, forty times over. This drill removes that cost.
The single highest-value table in the quantitative section.
- 0
- Correct
- 0
- Answered
- 0%
- Accuracy
- 0.0s
- Per question
The arithmetic behind the advice
A caselet or table set in a banking paper typically needs somewhere between ten and fifteen percentage operations across its five questions. Assume you are slow but not hopeless at these, taking six seconds each. That is roughly seventy-five seconds spent on conversions in a single set, in a section where you have about forty seconds per question in total.
Now assume the same values are automatic, at one second each. You have recovered a full minute inside one set, and there are usually three or four sets. The gain across the paper is three to four minutes, which is five to eight additional questions you have time to attempt. There is no study technique in quantitative aptitude with a better return per hour invested than memorising a table of fifteen numbers.
The table worth knowing cold
| Fraction | Percentage | Where it shows up |
|---|---|---|
| 1/3 | 33.33% | Ratio splits, profit and loss |
| 1/6 | 16.67% | Time and work, discounts |
| 1/7 | 14.29% | Data interpretation shares |
| 1/8 | 12.5% | Discounts, simple interest |
| 1/9 | 11.11% | Percentage increase questions |
| 1/11 | 9.09% | Growth and decline in DI |
| 1/12 | 8.33% | Monthly shares of an annual figure |
| 1/13 | 7.69% | Approximation questions |
| 1/14 | 7.14% | Approximation questions |
| 1/15 | 6.67% | Time and work |
| 1/16 | 6.25% | Successive discounts |
Learn the unit fractions and the multiples follow. Once 1/8 is 12.5 per cent, 3/8 is three of those, 37.5 per cent, without any calculation at all. The full treatment, including the squares and the percentage change shortcuts, is in the article below.
Frequently asked questions
Why drill fractions rather than practise more questions?
Because in a data interpretation set the arithmetic is not the difficulty, it is the tax. A set with five questions might need twelve percentage conversions. If each one costs you eight seconds of thought, you have spent a minute and a half on work that carries no marks. Candidates who know the fraction table finish the same set in three minutes and use the remaining time on questions that actually distinguish them.
How fast should I be?
Under four seconds per value with accuracy above ninety per cent. At that point recall is automatic rather than calculated, which is the property you want: it frees your attention for the structure of the question instead of the number crunching inside it.
Is an on-screen calculator not provided?
In IBPS PO mains, yes, and in RRB NTPC there is none at all. Even where a calculator exists, reaching for it costs more time than recalling that three-eighths is 37.5 per cent. The calculator is for long multiplications, not for conversions you should know.
How long does it take to learn the table?
Two weeks of ten minutes a day is enough for most people to become fluent up to the twenty-fifths. It is one of the highest returns on time available anywhere in quantitative preparation, because the same values recur in every single paper.
Related reading
- Calculation speed: fractions, squares and percentage change— the full tables and the methods behind them.
- How to approach a data interpretation set— where this speed gets spent.
- Daily quiz— ten questions a day, under a clock.