In this guide
A chart DI set asks the same questions as a table set: percentage change, share, ratio, average. The difference is the first step. You have to pull numbers out of a picture, and the picture can mislead. A tall bar on a stretched scale, a line that falls while the value keeps rising, a pie slice that looks like a quarter but is 22%: each of these costs marks before any calculation begins.
Chart sets appear in both the prelims and the mains. In the prelims, a set of about five questions is common. In the mains, charts are often combined, for example a bar chart of totals with a pie chart of shares, and questions need both.
Reading bar and line charts
- Check the axis scale and units. Is it thousands or lakh? Does the axis start at zero? If the axis starts at 40, a bar of 60 looks twice as tall as a bar of 50, yet it is only 20% larger.
- Read values at the gridlines. When a bar ends between gridlines, the question usually gives options wide enough for a sensible estimate.
- Read the legend. With two or three series, confirm which colour is which before the first question.
- For lines, the slope shows absolute change, not percentage change. A rise from 20 to 30 looks the same as a rise from 80 to 90, but one is 50% and the other 12.5%.
Worked set 1: a two-series bar chart
The figures below are made up for practice.
Sales of laptops and tablets by a company (thousand units)
| Year | Laptops | Tablets |
|---|---|---|
| 2021 | 40 | 25 |
| 2022 | 48 | 30 |
| 2023 | 36 | 45 |
| 2024 | 54 | 36 |
| 2025 | 60 | 40 |
Q1. What is the percentage increase in laptop sales from 2023 to 2024?
- (54 − 36) ÷ 36 × 100 = 18 ÷ 36 × 100 = 50%.
Q2. In which year was the ratio of tablets to laptops the highest?
- 2021: 25/40 = 0.625. 2022: 30/48 = 0.625. 2023: 45/36 = 1.25. 2024: 36/54 = 0.67. 2025: 40/60 = 0.67.
- 2023, the only year tablets outsold laptops.
Q3. What were the average combined sales per year?
- Yearly totals: 65, 78, 81, 90, 100. Sum = 414.
- 414 ÷ 5 = 82.8 thousand.
Q4. Tablet sales in 2023 were what percentage more than in 2022?
- (45 − 30) ÷ 30 × 100 = 50%.
Q5. What is the difference between average laptop sales and average tablet sales over the five years?
- Laptops: 238 ÷ 5 = 47.6. Tablets: 176 ÷ 5 = 35.2.
- Difference = 12.4 thousand.
The growth-rate line: the trap that catches most people
Some line charts plot percentage growth over the previous year, not the value itself. On such a chart, a falling line does not mean the value fell. It means the value grew more slowly. The value falls only when the line goes below zero.
Worked set 2: a percentage-growth line chart
The figures below are made up for practice.
Growth in a bank's deposits over the previous year (%). Deposits in 2021 were ₹500 crore.
| Year | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|
| Growth over previous year | 20% | 10% | 25% | −4% |
First convert the growth rates into values. Each year's value is the previous year's value multiplied by (1 + growth/100).
| Year | Calculation | Deposits (₹ crore) |
|---|---|---|
| 2022 | 500 × 1.20 | 600 |
| 2023 | 600 × 1.10 | 660 |
| 2024 | 660 × 1.25 | 825 |
| 2025 | 825 × 0.96 | 792 |
Q1. Were deposits lower in 2023 than in 2022?
- No. The line falls from 20% to 10%, but 10% growth is still growth. Deposits rose from ₹600 crore to ₹660 crore.
Q2. In which year were deposits the highest?
- 2024 (₹825 crore). 2025 was the only year of decline.
Q3. What was the percentage increase in deposits from 2021 to 2024?
- 825 ÷ 500 = 1.65, so 65%.
- Adding the rates (20 + 10 + 25 = 55%) is wrong, because growth compounds.
Q4. What were the average deposits from 2022 to 2025?
- (600 + 660 + 825 + 792) ÷ 4 = 2,877 ÷ 4 = ₹719.25 crore.
Pie charts: per cent and degrees
A pie chart shows how a whole is split. It may be labelled in per cent or in degrees.
| Conversion | Formula |
|---|---|
| Per cent to degrees | per cent × 3.6 |
| Degrees to per cent | degrees ÷ 3.6 |
| Amount from per cent | per cent × total ÷ 100 |
| Amount from degrees | degrees × total ÷ 360 |
Why 3.6: the whole circle is 360° and the whole is 100%, so 1% corresponds to 360 ÷ 100 = 3.6°.
When the pie is in degrees, find the value of one degree first. Every later question becomes one multiplication.
Worked set 3: a pie chart in degrees
The figures below are made up for practice.
A college's annual budget of ₹36 lakh, by head
| Head | Central angle |
|---|---|
| Salaries | 144° |
| Infrastructure | 72° |
| Laboratories | 54° |
| Library | 36° |
| Miscellaneous | 36° |
| Events | 18° |
One degree = 36,00,000 ÷ 360 = ₹10,000.
Q1. How much is spent on salaries?
- 144 × 10,000 = ₹14.4 lakh.
Q2. What percentage of the budget goes to the library?
- 36 ÷ 3.6 = 10%.
Q3. How much more is spent on laboratories than on events?
- (54 − 18) × 10,000 = ₹3.6 lakh.
Q4. What is the ratio of infrastructure spending to library and events spending together?
- 72 : (36 + 18) = 72 : 54 = 4 : 3.
Q5. Next year the budget rises by 25% but the salary amount stays the same. What will the central angle for salaries be?
- New budget = 36 × 1.25 = ₹45 lakh.
- Angle = 14.4 ÷ 45 × 360 = 115.2°.
Common traps
- Comparing slices across two pies. A 20% slice of ₹50 lakh is bigger than a 25% slice of ₹30 lakh. Compare amounts, not percentages, when totals differ.
- Trusting bar heights. Check whether the axis starts at zero.
- Adding growth rates. Successive growth multiplies. See the percentage guide for the a + b + ab/100 rule.
- Mixing up series. On a two-colour bar chart, re-check the legend when a question switches products.
Practice set
Use set 1 for questions 1 to 3, set 2 for questions 4 and 5, and set 3 for questions 6 to 8.
- What is the percentage increase in laptop sales from 2021 to 2025?
- Tablet sales in 2024 were what percentage of laptop sales in 2024 (to one decimal place)?
- In which year did combined sales rise by the largest amount over the previous year?
- By how much did deposits fall from 2024 to 2025?
- What was the percentage increase in deposits from 2021 to 2025?
- What percentage of the budget goes to salaries and laboratories together?
- How much is spent on miscellaneous items?
- If the events budget is doubled next year and everything else stays the same, what is the new total budget?
Answers:
- 50%. (60 − 40) ÷ 40 × 100.
- 66.7%. 36 ÷ 54 × 100.
- 2022. Rises over the previous year: 2022 +13, 2023 +3, 2024 +9, 2025 +10 (thousand).
- ₹33 crore. 825 − 792.
- 58.4%. 792 ÷ 500 = 1.584.
- 55%. (144 + 54) ÷ 3.6 = 198 ÷ 3.6.
- ₹3.6 lakh. 36 × 10,000.
- ₹37.8 lakh. Events rise from ₹1.8 lakh to ₹3.6 lakh, adding ₹1.8 lakh.
What to do next
- Solve one chart set a day for ten days, mixing bar, line and pie.
- For every line chart, first ask: does it plot values or growth rates?
- For every pie in degrees, write the value of 1° before the first question.
- Revise table DI for the calculation shortcuts, then move to caselet DI.
A note on dates and numbers. Exam patterns, vacancies and schedules change from year to year. Always confirm the current details in the latest notification on the Institute of Banking Personnel Selection website .
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