Data Interpretation
🔒 Log in to trackReading tables and charts: totals, percentage change, pie-chart angles and shares, row averages, weighted averages and successive growth. DI rewards calm reading more than calculation — every question is one fraction or one product away, and the data is given in clean, round numbers by design. Tier 2 sets often attach a 5-question block to one table, so per-table setup pays twice.
One page per subtopic: detailed notes, every question type, formulas, tricks and practice sets.
Every formula on one printable page, grouped by subtopic.
5 exam-level questions worked step by step.
67 questions — untimed practice or a timed test with analysis.
Track record in the exam
Questions per shift in recent SSC CGL papers.
Test difficulty mix (67 questions)
Question patterns exams keep repeating
Taken from previous-year papers. If a pattern is marked "very common", expect to see it in your exam.
Totals and differences from a table
very common"Find the total of a row or column" or "the gap between two cells".
Add the numbers in friendly pairs.
Check the unit (thousand, crore) before picking the option.
Production of cars (in thousands) by four companies:
| Year | P | Q | R | S |
|---|---|---|---|---|
| 2019 | 120 | 90 | 150 | 80 |
| 2020 | 135 | 110 | 145 | 95 |
| 2021 | 150 | 105 | 160 | 100 |
| 2022 | 140 | 125 | 170 | 110 |
| 2023 | 165 | 130 | 175 | 120 |
The total production of company R over the five years is:
R: 150, 145, 160, 170, 175
150 + 145 = 295
160 + 170 + 175 = 505
295 + 505 = 800 thousand
Percentage change between two years
very common"What is the percentage increase from 2022 to 2023?"
Find the change: new − old.
Divide by the OLD value, then multiply by 100.
Annual sales of a company (₹ crore):
| Year | 2019 | 2020 | 2021 | 2022 | 2023 |
|---|---|---|---|---|---|
| Sales | 160 | 200 | 260 | 250 | 320 |
The percentage increase in sales from 2022 to 2023 is:
Change = 320 − 250 = 70
70 ÷ 250 = 0.28
0.28 × 100 = 28%
Pie chart: angle to value
very commonA pie chart with angles (or %) and a stated total; asks the value of one sector.
Find what 1° is worth: total ÷ 360.
Multiply by the sector's angle.
A pie chart shows a family's monthly budget of ₹72,000. The central angles are:
| Head | Food | Rent | Education | Transport | Savings | Others |
|---|---|---|---|---|---|---|
| Angle | 108° | 72° | 54° | 36° | 45° | 45° |
The amount spent on Rent is:
1° = 72,000 ÷ 360 = ₹200
Rent angle = 72°
72 × 200 = ₹14,400
Ratios and "what percent of"
common"Sales in 2020 are what percent of sales in 2023?" or "ratio of X to Y".
X as a percent of Y: divide X by Y, then multiply by 100.
For a ratio, write X : Y and cancel common factors.
Annual sales of a company (₹ crore):
| Year | 2019 | 2020 | 2021 | 2022 | 2023 |
|---|---|---|---|---|---|
| Sales | 160 | 200 | 260 | 250 | 320 |
The sales in 2020 are what percent of the sales in 2023?
X = 200 and Y = 320 (the one after "of")
200 ÷ 320 = 0.625
0.625 × 100 = 62.5%
Averages and weighted averages
commonAverage of a row or column, or groups with different sizes and averages to combine.
One row: add, then divide by how many.
For groups, use totals (people × average). Never just average the averages.
A company has four departments. The table shows the number of employees and their average salary:
| Department | Employees | Average salary |
|---|---|---|
| A | 40 | ₹25,000 |
| B | 30 | ₹32,000 |
| C | 20 | ₹28,000 |
| D | 30 | ₹40,000 |
The average salary of departments A and B together is:
A: 40 × 25,000 = ₹10 lakh
B: 30 × 32,000 = ₹9.6 lakh
Total ₹19.6 lakh for 70 people: 19.6 lakh ÷ 70 = ₹28,000
Answer ₹28,000 (not the plain 28,500)
Growth over several years
commonGrowth rates for several years, or a rise followed by another rise or fall.
Start with 100.
Apply each change one after another. Never just add the percentages.
A price rises 10% and then another 10%. The net increase is:
Start: 100
Up 10% → 110
Up 10% of 110 (that is 11) → 121
100 became 121, so 21% more
Which year is highest or lowest
common"In which year was the difference the least?" or "in how many years was X above average?"
Work out the asked number for every year and list them.
Then pick the smallest or biggest (or count).
Production of cars (in thousands) by four companies:
| Year | P | Q | R | S |
|---|---|---|---|---|
| 2019 | 120 | 90 | 150 | 80 |
| 2020 | 135 | 110 | 145 | 95 |
| 2021 | 150 | 105 | 160 | 100 |
| 2022 | 140 | 125 | 170 | 110 |
| 2023 | 165 | 130 | 175 | 120 |
In which year was the difference between the production of R and S the least?
2019: 150 − 80 = 70
2020: 145 − 95 = 50
2021: 60, 2022: 60, 2023: 55
Smallest gap is 50, so 2020
Two pie charts with different totals
occasionalTwo pies (two years or two firms), each with its own total; asks how one item changed.
Find the actual value from each pie: share × that pie's total.
Compare the values, not the shares.
Exports: 2022 total ₹400 crore with Asia 30%; 2023 total ₹500 crore with Asia 27%. The change in exports to Asia is:
2022: 30% of 400 = 120
2023: 27% of 500 = 135
Change = 135 − 120 = 15
Exports rose by ₹15 crore, even though the share fell