Data Interpretation (Tables & Charts)

Scenario

Reading DI questions is exactly like reading a Zepto operational dashboard during peak IPL hours. You have a massive table of riders, zones, and delivery times:

| Zone | Active Riders | Avg Delivery Time |

|------|---------------|-------------------|

| Kormangala | 450 | 14m |

| Indiranagar| 320 | 18m |

Your job is not to calculate every single cell - it is to spot the bottleneck instantly using rough ratios and percentage jumps.

Mental model

DI is just basic percentages, ratios, and averages hidden inside visual noise.

Data Interpretation tests your ability to extract relevant data from tables, bar graphs, pie charts, and line graphs, and perform quick approximations rather than precise calculations.

Formula

Percentage Change = (New - Old) / Old x 100. Ratio comparison: A/B vs C/D - cross-multiply (A x D vs B x C). Pie chart: Degrees to % = Degrees / 3.6. % to Degrees = % x 3.6. Average = Sum / Count. The workflow: Read question -> Locate only the needed cells -> Approximate -> Eliminate options.

In a pie chart, 1% = 3.6 degrees. For line graphs, the slope indicates rate of growth. For bar charts, compare bar heights visually before computing. Never calculate exact values unless the answer choices are dangerously close to each other.

Worked example

Problem: A table shows a startup's monthly active users: Jan=80,000, Feb=92,000, Mar=110,400. (a) What is the % growth Jan to Feb? (b) Which month had the higher growth rate?

1. Set up: We need % growth for each period. Formula: (New - Old) / Old x 100.
2. Jan to Feb: (92000 - 80000) / 80000 x 100 = 12000 / 80000 x 100 = 15%.
3. Feb to Mar: (110400 - 92000) / 92000 x 100 = 18400 / 92000 x 100 = 20%.
4. Approximate check: 15% of 80k = 12k (correct). 20% of 92k = 18.4k (correct).
5. Answer: Feb had 15% growth, Mar had 20% growth. Mar showed the higher growth rate.

Answer: Jan-Feb growth: 15%. Feb-Mar growth: 20%. March had the higher growth rate.

Problem: In a pie chart of a company's expense budget (total = Rs1,20,000), the 'Salaries' sector spans 150 degrees. What is the salary expenditure?

1. Set up: Convert degrees to percentage. 150 degrees / 3.6 = 41.67%.
2. Apply percentage to total: 41.67% of 1,20,000 = 0.4167 x 1,20,000 = 50,000.
3. Sanity-check: 150 out of 360 degrees = 5/12 of the total. 1,20,000 x 5/12 = 50,000. Matches.

Answer: Salary expenditure is Rs50,000.

Shortcuts

• The Approximation Rule: If options are spaced out (e.g., 10%, 15%, 20%), round numbers heavily. 412/1987 becomes 400/2000 = 1/5 = 20%. (Finding 18.2% of 498? Just find 20% of 500 (100) and subtract a little.)
• Pie Chart Degree to Percentage: To convert degrees to percentage, divide by 3.6. To convert percentage to degrees, multiply by 3.6. (72 degrees on a pie chart = 72 / 3.6 = 20%.)
• Ratio Stacking: When comparing two huge fractions A/B and C/D, compare the percentage growth of numerators vs denominators, or cross-multiply. (Compare 145/290 vs 160/310. First is exactly 50%. Second: 160 > 155 (half of 310), so 160/310 > 50%. Second is larger.)

Common mistakes

• Calculating Everything: Do not calculate values for all years/categories. Only calculate what the specific question needs.
• Confusing 'Percentage More' with 'Percentage Of': If A is 150 and B is 100, A is 150% OF B, but A is only 50% MORE than B.

Glossary

interpretation

Understanding and explaining what information means.

approximations

Rough guesses or estimates that are close enough to the exact answer.

expenditure

The total amount of money spent on something.

Recall questions

• A pie chart sector is 108 degrees. What percentage of the total does it represent?
• If Company A's revenue grew from 400 to 500, what is the percentage growth?
• How do you quickly approximate 349 / 6980?

Questions & answers

A table shows revenue: 2021 (420M), 2022 (480M), 2023 (550M). What is the approximate average annual percentage growth rate?

14.5%

Approach: 2021->2022 is ~14.3% (60/420). 2022->2023 is ~14.6% (70/480). Average is around 14.5%.

In a pie chart of expenses (Total = 50,000), 'Marketing' is represented by 54 degrees. What is the expenditure on Marketing?

7,500

Approach: 54 degrees = 54/3.6 = 15%. 15% of 50,000 = 7,500.

Continue learning

Previous: Mean, Median, Mode & Dispersion

Return to Aptitude Roadmap