CSAT
Data Interpretation
CSAT
Data Interpretation — Quick Revision
One-page CSAT revision of data interpretation: core formulas, table and graph reading rules, pie-chart conversions, approximation shortcuts and data sufficiency.
SyllabusCSAT · Data interpretation (charts, graphs, tables, data sufficiency) — Class X level
Everything you need to keep in mind before opening a CSAT data-interpretation set.
Core Formulas
| Asked for | Formula |
|---|---|
| Percentage change | $\dfrac{\text{New} - \text{Old}}{\text{Old}} \times 100$ |
| Share of total | $\dfrac{\text{Part}}{\text{Total}} \times 100$ |
| Average | Sum ÷ count |
| Ratio | Simplify by the HCF |
| Pie-chart value | $\dfrac{\text{Angle}}{360^\circ} \times \text{Total}$ |
| Pie-chart angle | Percentage × $3.6^\circ$ |
Pie-Chart Conversions
| % | 5 | 10 | 12.5 | 15 | 20 | 25 | 30 | 50 |
|---|---|---|---|---|---|---|---|---|
| Angle | 18° | 36° | 45° | 54° | 72° | 90° | 108° | 180° |
Reading Rules
High-yield reading rules
- Read the title, unit and base year before any calculation.
- The base of a percentage change is the earlier value.
- Largest absolute increase ≠ largest percentage increase.
- The steepest line segment shows the largest absolute change.
- Pie charts of different years show shares; amounts need the totals.
- Percentage points measure absolute change in a rate; per cent measures relative change.
Approximation
| Tool | Use |
|---|---|
| Fraction table | $\tfrac{1}{6} = 16.67\%$, $\tfrac{1}{7} \approx 14.29\%$, $\tfrac{1}{8} = 12.5\%$, $\tfrac{1}{9} \approx 11.11\%$ |
| Cross-multiplication | Compare $\tfrac{a}{b}$ and $\tfrac{c}{d}$ via $ad$ vs $bc$ |
| 10% / 1% split | 41% of 615 ≈ 246 + 6.15 |
| Round only if options are far apart | Within about 2%, calculate precisely |
Data Sufficiency
| Outcome | When |
|---|---|
| Statement 1 alone | 1 fixes a single answer, 2 does not |
| Statement 2 alone | 2 fixes a single answer, 1 does not |
| Either alone | Each fixes the answer by itself |
| Both together | Neither alone, but combined they fix it |
| Neither | Even combined, more than one answer remains |
Traps
Four classic errors
- Dividing by the later value for percentage change.
- Ignoring units (thousands vs lakhs vs crores).
- Comparing pie-chart shares across years as if they were amounts.
- Using outside assumptions in data sufficiency.
Related Topics
- Data Interpretation: Tables, Graphs and Data Sufficiency
- Data Interpretation — practice questions
- Percentages, Ratio and Averages — quick revision
- All quick-revision sheets
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