What the exam asks
DI is the highest-weight topic: 10 to 15 questions across Prelims and Mains. Expect tables, bar graphs, line graphs, pie charts, caselets (data written as a paragraph), missing-data tables and, in Mains, mixed charts (a pie plus a table). A set of 5 questions should take about 4 to 5 minutes.
Core formulas
| Asked | Formula |
|---|---|
| Percentage change | (New - Old)/Old x 100 |
| A is what % of B | A/B x 100 |
| A is what % more than B | (A - B)/B x 100 |
| Pie value | Total x sector % / 100 |
| Central angle | sector % x 3.6 degrees |
| Sector % from angle | angle / 3.6 |
| Average | Sum / number of items |
| Ratio | cancel common factors (the total cancels within one pie) |
Pie chart tricks
- Within one pie, compare percentages directly; convert to values only at the end.
- Difference of two sectors = (difference of %) x total.
- If the pie is of expenditure but the question is about income, convert carefully - this is a favourite trap.
- When two pies have different totals, you cannot compare their percentages directly.
Caselets
- Read the paragraph once and build a small table of every quantity.
- Fill derived values (remainders, totals) immediately.
- Most caselet questions then become one-line calculations.
Missing-data tables
Each row hides one or two values that can be found from the others (for example Produced = Sold + Unsold, and % Sold = Sold/Produced x 100). Fill only the cells the question needs; do not complete the whole table first.
Worked example
A company's expenditure of Rs. 2,40,000 is split: Salary 35%, Rent 15%, Others 50%.
- Rent = 15% of 2,40,000 = Rs. 36,000.
- Central angle of Rent = 15 x 3.6 = 54 degrees.
- Salary exceeds Rent by (35 - 15)% of 2,40,000 = Rs. 48,000.
- Salary is (35 - 15)/15 x 100 = 133.33% more than Rent.
Calculation shortcuts
- Use fraction equivalents: 37.5% = 3/8, 62.5% = 5/8, 16.67% = 1/6.
- For "approximately what percent", round the denominator first.
- Average of values: subtract a convenient base from each, average the deviations, add back.
- Ratios: cancel common zeros and common totals before dividing.
Common traps
- Percentage points vs percent: 30% to 25% is a fall of 5 points but 16.67%.
- "More than" uses the smaller value as base; "less than" uses the larger.
- Units: lakh vs crore, thousands in tables, per kg vs per quintal.
- Simple average of rates (e.g. NPA %) is not the same as the weighted overall rate.
Time target: 50 to 60 seconds per DI question. Solve the easiest set in the paper first; DI sets vary a lot in difficulty.