Data Interpretation: Tables, Charts and Smart Approximation

Data interpretation (DI) sets present data in tables and charts and ask several questions. They reward calm reading and quick approximation.

Types of data

Type	What to watch
Table	rows and columns; units; totals
Bar chart	heights; groups; scale on the axis
Line graph	trends over time; steepness
Pie chart	shares of a whole, in percentages or degrees
Mixed sets	two data sources that must be combined

Before you calculate

1. Read the title and axis labels.
2. Check the units (thousands, millions, percentages).
3. Note the scale. A truncated axis can mislead.
4. Read all the questions first to see what you need.

Pie charts

A full circle is 360 degrees.

• Angle for a share = percentage × 3.6.
• Percentage from an angle = angle ÷ 3.6.

Example: A sector of 72° represents 72 ÷ 3.6 = 20%.

Percentage change

Percentage change = (new − old) ÷ old × 100.

Example: Sales rose from 250 to 300. Change = 50 ÷ 250 = 20%.

Ratios and averages

Many questions ask for ratios or averages between categories. Write them clearly and simplify.

Smart approximation

DI questions often allow rounding. Approximate to save time:

• Round numbers to the nearest ten or hundred.
• Compare fractions by cross-multiplying instead of dividing.
• Estimate percentages using benchmarks: 10%, 25%, 50%.

Example: 47 out of 190 is close to 50 out of 200 = 25%.

Check whether the options are far enough apart to allow rough estimation.

Common traps

1. Reading the wrong row or column.
2. Mixing units.
3. Percent versus percentage points.
4. Assuming data that isn't shown.

Time management

• Spend about a minute reading the data.
• Answer easy questions first.
• Skip lengthy calculations if they'd take too long, and return if you have time.

Practice

Do one small DI set daily, and time yourself. Familiarity with layouts speeds reading.

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