Data Interpretation

medium importance~2 Q in Tier 116 formulas⚡ 10 shortcuts5 subtopics

Overview Learn (5)Formulas (16)Examples (5)Practice (67)

Reading 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.

📖

Learn — 5 subtopics

One page per subtopic: detailed notes, every question type, formulas, tricks and practice sets.

⚡

Formula sheet

Every formula on one printable page, grouped by subtopic.

✍️

Solved examples

5 exam-level questions worked step by step.

🎯

Practice & test

67 questions — untimed practice or a timed test with analysis.

Track record in the exam

avg 3.5 Q / shift2024: 3–4 Q2025: 3–4 Q

Questions per shift in recent SSC CGL papers.

Test difficulty mix (67 questions)

20 easy33 medium14 hard

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

Spot it:

Sum a row/column, or find the gap between two cells, two years or two companies. The most basic DI ask, and the first question of most table sets.

How to solve: Add in friendly pairs and keep subtotals in the margin; for a difference of totals, subtract the totals once instead of cell by cell. Check the unit (thousand, lakh) before choosing the option.

Example: 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:

$150 + 145 + 160 + 170 + 175 = 800$ thousand.

Learn this in “Reading tables: totals, differences, ratios” →

Percentage change between periods

very common

Spot it:

'The percent increase from year A to year B', often with 'approximately' in the question, or 'by what percent is X more than Y'.

How to solve: $\frac{\text{new}-\text{old}}{\text{old}}\times100$ with the base as the earlier (or 'than') value; keep the fraction until the end and match the nearest option.

Example: 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:

$\frac{320-250}{250}\times100 = 28\%$ .

Learn this in “Percentage change and comparisons” →

Pie-chart sector values

very common

Spot it:

Sectors printed as degrees or percentages with a stated total; a value, a share or an angle asked.

How to solve: Value $= \frac{\theta}{360}\times$ total; angle $= \% \times 3.6^\circ$ . Find the worth of $1^\circ$ once and reuse it; add angles before converting when two sectors are asked together.

Example: 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:

$1^\circ = \frac{72000}{360} = ₹200$ , so Rent $= 72 \times 200 = ₹14{,}400$ .

Learn this in “Pie charts: degrees, shares and totals” →

Ratios and shares

common

Spot it:

'Ratio of X to Y in year Z', 'X is what percent of Y', or the share of two heads of a total taken together.

How to solve: Reduce the ratio fraction directly (cancel the HCF) and keep the order asked; for shares, add the parts first, then divide by the total once.

Example: 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?

$\frac{200}{320} \times 100 = 62.5\%$ .

Learn this in “Percentage change and comparisons” →

Averages and weighted averages

common

Spot it:

Row/column averages over the years, or a table of group sizes with group averages to combine.

How to solve: Simple mean of the cells for one row/column; for groups, weight by size: $\frac{n_1\bar{x}_1 + n_2\bar{x}_2}{n_1+n_2}$ . The plain average of the group means is the planted trap.

Example: 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:

$\frac{40 \times 25000 + 30 \times 32000}{70} = ₹28{,}000$ , not the plain $28{,}500$ .

Learn this in “Averages from data” →

Successive growth / reverse growth

common

Spot it:

Multi-year growth rates with the final (or initial) value given; sometimes a rise followed by a fall.

How to solve: Multiply factors $(1 \pm \frac{a}{100})$ to move forward; divide the final value by the factor to move back. Never add percentages across years.

Example: A price rises 10% and then another 10%. The net increase is:

$1.1 \times 1.1 = 1.21$ → net $+21\%$ , not 20%.

Learn this in “Growth rates and successive changes” →

Maximum / minimum year, and counting years

common

Spot it:

'In which year was the difference/growth the least?' or 'in how many years was X above its average'.

How to solve: Compute the small derived number (gap, total, rate) for each year and list it in the margin, then pick. For counting, fix the benchmark once; values equal to it do not count for 'more than'.

Example: 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?

Gaps: 70, 50, 60, 60, 55 — least is 50 in 2020.

Learn this in “Reading tables: totals, differences, ratios” →

Two pie charts with different totals

occasional

Spot it:

Two pies (two years, two firms), each with its own total; a change or ratio of one item asked.

How to solve: Convert the item to a value in each pie using its own total, then compare values. Shares alone mislead: a falling share on a bigger pie can still be a bigger amount.

Example: Exports: 2022 total ₹400 cr with Asia 30%; 2023 total ₹500 cr with Asia 27%. The change in exports to Asia is:

$120 \to ₹135$ cr: a rise of ₹15 crore (12.5%) even though the share fell.

Learn this in “Pie charts: degrees, shares and totals” →

Your next step

New here? Start with subtopic 1 in Learn. Revision mode? Jump straight to the test and let it tell you what to fix.