A method that works for every chart
- Read the title, units and labels before the questions.
- Read the question and decide which two or three numbers it needs.
- Compute only those, using ratios or approximation where options allow.
- Check units in the answer (thousands, crores, percentages).
Types of charts
| Type | Typical question | Watch for |
|---|---|---|
| Table | Totals, differences, percentage change | Units; the base of percentages |
| Bar chart | Compare categories or years | Axis scale; stacked vs grouped bars |
| Line graph | Growth and trends | Where lines cross; non-zero axis |
| Pie chart | Share of a total; angles | 360° = 100%; whether the values are percentages or amounts |
| Caselet | Data in a paragraph | Build your own table first |
Worked examples
Sales (in units) of two products over three years:
| Product | Year 1 | Year 2 | Year 3 |
|---|---|---|---|
| A | 200 | 250 | 300 |
| B | 150 | 180 | 240 |
Q1. Percentage growth in A's sales from Year 1 to Year 3: (300 − 200) ÷ 200 = 50%.
Q2. Ratio of A's to B's total sales: A = 750; B = 570; 750 : 570 = 25 : 19.
Q3. Year in which B's growth over the previous year was highest: Year 2: 30 ÷ 150 = 20%; Year 3: 60 ÷ 180 = 33.3%. So Year 3.
Pie chart. A pie chart shows a company's expenses, with a sector for salaries of 126°. Share = 126 ÷ 360 = 35%. If total expenses are 8 crore, salaries are 2.8 crore.
Comparing fractions without dividing. To compare 37/90 and 41/100: 37 × 100 = 3,700; 41 × 90 = 3,690; so 37/90 is slightly larger.
Approximation tricks
- Round to friendly numbers when options are far apart: 198 to 243 is about 200 to 240, so 20% (exact 22.7%).
- Use fractions: 33.3% = 1/3.
- For percentage of a total, compute the fraction first and convert at the end.
- Cross-multiply to compare ratios.
Common traps
- Misreading units (thousands vs lakhs).
- Using the wrong base for percentages.
- Misreading a stacked bar.
- Calculating exactly when an estimate would do.
- Not noticing a truncated axis.
A practice routine
- Week 1: calculation tools (percentages, fractions, ratios) for ten minutes a day, and one untimed table set.
- Week 2: one timed set a day at 8 minutes.
- Week 3: approximation drills; two sets a day.
- Week 4: mixed sets, choose the order and review.
More method in how to practise data interpretation faster.
Where it appears
Data interpretation appears in banking, CAT DILR, XAT, MAT, SSC CGL and CLAT papers. Strengthen percentage and averages first.
Practice tests below are published by institutes and educators on TestMint.
