Data Interpretation Notes for SSC Exams

Data Interpretation (DI) tests how fast you can read data from tables and graphs and calculate percentages, ratios and averages. Five questions usually come from DI in SSC CGL Tier 1, and it is also part of Tier 2. These data interpretation notes for SSC explain the types of charts, the formulas and the steps to solve a set quickly, with solved examples and practice questions.

Types of Data Interpretation Sets

• Table: data in rows and columns.
• Bar graph: bars of different heights for different items or years.
• Line graph: points joined by a line to show a trend over time.
• Pie chart: a circle divided into sectors, with a total of 360 degrees (or 100%).
• Mixed DI: a table with a graph, or two charts together.

Important DI Formulas

Sample Data Set

Read the following sales data (in units) of a company and use it for the examples and the practice questions below.

Steps to Solve a DI Set Quickly

1. Read the title, the units and the headings of the table or chart first.
2. Skim the questions to see which values are needed.
3. Do not calculate everything; calculate only what each question asks.
4. Round the numbers when the options are far apart (approximation).
5. Use the percentage and ratio shortcuts from the percentage and ratio chapters.

Approximation and Calculation Shortcuts

• To find 25% of a number, divide by 4; for 12.5%, divide by 8; for 20%, divide by 5.
• To compare two ratios, compare their decimal values or cross-multiply.
• For a percentage of a large number, round off to a convenient number and use the nearest option.
• In a pie chart, 10% = 36 degrees, 25% = 90 degrees and 50% = 180 degrees.
• For growth over several years, add the percentage changes only when they are small; otherwise use the successive change formula.

Solved Examples

Example 1: Using the data above, find the percentage increase in sales from 2021 to 2022.
Solution: Increase = 250 - 200 = 50. Percentage = 50 / 200 x 100 = 25%.

Example 2: Find the average sales of the five years.
Solution: Total = 200 + 250 + 300 + 270 + 350 = 1370. Average = 1370 / 5 = 274 units.

Example 3: In which year was the percentage growth over the previous year the highest?
Solution: Growth: 2022 = 25%, 2023 = 20%, 2024 = -10%, 2025 = 80/270 = 29.6%. The highest growth was in 2025.

Example 4: Find the ratio of sales in 2023 to that in 2021.
Solution: 300 : 200 = 3 : 2.

Example 5: Find the percentage fall in sales from 2023 to 2024.
Solution: Fall = 30. Percentage = 30 / 300 x 100 = 10%.

Example 6: In a pie chart of total expenditure Rs 3,600, an item takes 20%. Find the angle of its sector.
Solution: Angle = 20% of 360 = 72 degrees.

Quick Tips to Solve Faster

• Always check the units (thousands, lakhs, crores or percentage) before calculating.
• Use approximation when the options are far apart.
• For percentage change, always divide by the old value.
• In pie charts, the total is 360 degrees, so 1% = 3.6 degrees.
• Do not waste time on lengthy calculations; skip a question if it takes more than a minute.

Common Mistakes to Avoid

• Dividing by the new value instead of the old value for percentage change.
• Mixing the units in the table and the question.
• Confusing percentage points with percentage change.
• Reading the wrong row or column from the table.
• Not converting the angle of a pie chart into a percentage or value correctly.

Quick Revision Points

• Percentage change = change / old value x 100.
• Average = sum / number of items.
• Pie chart: angle = value / total x 360.
• 1% in a pie chart = 3.6 degrees.
• Read the units and the title before solving.

Practice Questions With Answers

1. Find the total sales of 2021 to 2025 in the data above.
   Answer: 1,370 units (200 + 250 + 300 + 270 + 350).
2. The sales of 2024 are what percentage of the sales of 2025 (approximately)?
   Answer: 77.1% (270 / 350 x 100).
3. Find the difference between the highest and the lowest sales.
   Answer: 150 units (350 - 200).
4. What is the central angle of a pie chart sector that represents 15%?
   Answer: 54 degrees (15 x 3.6).
5. Find the percentage increase in sales from 2021 to 2025.
   Answer: 75% (150 / 200 x 100).
6. Find the ratio of sales in 2022 to sales in 2024.
   Answer: 25 : 27 (250 : 270).
7. In a pie chart with a total of 7,200, a sector has a central angle of 90 degrees. Find its value.
   Answer: 1,800 (90 / 360 x 7200).
8. In a bar graph, A = 40 and B = 60. By what percentage is B more than A?
   Answer: 50% (20 / 40 x 100).
9. In how many years was the sales above the average of 274 units?
   Answer: 2 years (2023 and 2025).
10. If the sales in 2026 are 20% more than in 2025, find the sales in 2026.
    Answer: 420 units (350 x 1.2).

How to Practise This Chapter

1. Learn the formulas in the table until you can write them without looking.
2. Solve the solved examples again on your own, without reading the solution.
3. Attempt the practice questions above with a timer of 10 minutes.
4. Solve the matching SSC percentage practice paper to test yourself in exam style.
5. Check the previous year papers to see how SSC frames this topic.

Related Notes and Practice Papers

• Percentage Notes
• Average Notes
• Ratio and Proportion Notes
• Fractions and Decimals Notes
• SSC Percentage Practice Paper

Explore More SSC Subjects

SSC exams test many subjects, so connect this topic with the related subjects below:

• Reasoning Notes
• Statistics Notes
• Indian Economy Notes
• English Notes
• General Awareness Notes
• All SSC subjects and notes

Frequently Asked Questions

What is data interpretation?

Data interpretation is the skill of reading data given in tables, graphs and charts and answering questions based on it.

How many DI questions come in SSC CGL Tier 1?

Around five questions come from data interpretation in SSC CGL Tier 1.

What is the formula for percentage change?

Percentage change = (New value - Old value) / Old value x 100.

How do I find the angle in a pie chart?

Angle = (Value / Total) x 360 degrees.

How can I solve DI questions faster?

Read the questions first, calculate only what is asked, use approximation and revise the percentage and ratio shortcuts.

What is the difference between a bar graph and a line graph?

A bar graph shows values as bars, while a line graph joins points to show how a value changes over time.

What are percentage points?

The difference between two percentages is measured in percentage points, which is different from the percentage change.

How should I practise DI?

Solve one set daily with a timer, revise the formulas and practise the percentage practice paper.