Lessons / Quantitative aptitude
Quantitative aptitude · Day 8

Data Interpretation

DI is speed arithmetic on a table. Read the question first, then only the cells it needs; approximate with the fraction table.

Practise (8 questions) Present as slides

Why this topic matters

A chart is a question you answer by reading carefully. Half the marks in DI are lost by reading the wrong year, the wrong unit or the wrong bar.

DI sets carry 4 or 5 questions on one table or chart, so one set is worth a lot of marks. The maths is percentages, ratios and averages; the skill is reading.

Read before you calculate

Read the title, the units (thousands? lakhs? %?), the axes and the legend before the first question.

Then approximate: DI options are usually far enough apart that rounding to 2 significant figures is enough.

1202021150202213520231802024
Sales of a company (Rs crore)
Example 1From the chart: by what percent did sales grow from 2021 to 2024?
  1. Change = 180 - 120 = 60.Read the two bars.
  2. 60 / 120 × 100.Percentage change is over the earlier year.
  3. 50%.
Example 2Average sales over the four years?
  1. 120 + 150 + 135 + 180 = 585.
  2. 585 / 4 = 146.25 crore.

Pie charts

A pie chart shows shares of a whole. Sector angle = share × 360. A 90 degree sector is a quarter.

To get the actual value: share % × total.

30%Rent (30)25%Food (25)15%Travel (15)20%Savings (20)10%Other (10)
Monthly spending of a family (%)
Example 1If the family earns Rs 60,000 a month, how much more is spent on rent than on travel?
  1. Rent - travel = 30% - 15% = 15%.Work with the percentages first; multiply once.
  2. 15% of 60,000 = 9,000.
Example 2What is the angle of the Food sector?
  1. 25% of 360.
  2. = 90 degrees.

Tables and line charts

For a table, circle the row and column you need before calculating. For a line chart, the steepest segment is the biggest change, and a fall shows a line going down.

Ratios across years: compare using fractions of the same base, not by computing each value.

Formula summary

% growth
(new - old)/old × 100.
Share of total
part/total × 100. For a pie: part/total × 360 degrees.
Average across rows
Total / count.
Ratio
Reduce by HCF; compare by cross-multiplying, not by dividing.

Shortcuts and tricks

Growth % by fractions

Use it when: Old 120, new 150.

  1. 30/120 = 1/4 = 25%, no division needed.
Example120 → 150
  1. 1/4.

Before you move on, you should be able to...

  • read units and legends first
  • compute percentage change over the earlier value
  • turn pie percentages into values and angles

Practice questions (8)

Try each one before opening the solution. Or practise them one by one so your score is saved.

easy Sales (Rs crore) 2024 / 2025: A 120/150, B 200/210, C 80/104, D 160/144, E 140/175. Highest % growth?
  1. A 25, B 5, C 30, D -10, E 25.

Answer: C (30%)

easy Same table: average 2025 sales?
  1. 783 / 5.

Answer: 156.6

easy Same table: B's 2024 sales : E's 2025 sales?
  1. 200 : 175.

Answer: 8:7

easy Monthly budget Rs 60,000: rent 30%, food 25%, transport 10%, savings 20%, other 15%. Central angle for food?
  1. 25% of 360.

Answer: 90°

easy Same budget: by how much does food exceed transport?
  1. 15% of 60000.

Answer: Rs 9,000

medium Same table: overall % growth from 2024 to 2025 (2 d.p.)?
  1. 700 → 783: 83/700.

Answer: 11.86%

hard Same sales table: company B's share of total 2025 sales (2 d.p.)?
  1. 210 / 783.

Answer: 26.82%

hard Production (thousand units) 2021-2025: 40, 50, 45, 60, 72. Which year had the highest % growth over the year before?
  1. 2022 +25%, 2023 -10%, 2024 +33.3%, 2025 +20%.

Answer: 2024

Class plan (2 hours, for trainers)

A tested order for teaching this topic in one 2-hour session. Present mode follows the same order.

10 minWarm-up: percentage table.
20 minReading habits: title, units, legend.
25 minBar chart set.
25 minPie chart set with angles.
20 minTable and line chart sets.
15 minTimed DI set.
5 minRecap.
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