GRE Quantitative Aptitude – Bar & Pie Charts
Bar & pie charts are the most common visual data representations on the GRE Quant section.
They test your ability to interpret, compare, and manipulate numerical data quickly.
1. Quick Overview
| Chart Type | Purpose | How to Read |
|---|---|---|
| Bar Chart | Compare discrete categories | Look at the height (vertical bars) or length (horizontal bars). The axis gives the exact value. |
| Pie Chart | Show part‑to‑whole relationships | Each slice’s size (angle) represents a percentage of the total. |
Tip:
- Bar charts are best for exact values and direct comparisons.
- Pie charts are best for percentages and relative sizes.
2. Bar Charts
2.1 Structure
| Element | What it represents |
|---|---|
| X‑axis (horizontal) | Category labels |
| Y‑axis (vertical) | Value scale (units, percentages, etc.) |
| Bar height | Value of that category |
| Scale | Numbers at regular intervals (e.g., 0, 2, 4, 6) |
Common Variations
- Grouped (clustered) bars (side‑by‑side)
- Stacked bars (components of a whole)
2.2 How to Read
- Identify the scale on the axis.
- Locate the bar of interest.
- Read the value at the top of the bar (or at the end of a horizontal bar).
- Compare heights directly (no calculations needed).
- For missing bars: use the axis to infer the value if the bar is omitted.
2.3 Common GRE Questions
| Question Type | What to look for? |
|---|---|
| Exact value | Read the height. |
| Largest/smallest | Compare heights. |
| Total of several bars | Add the individual values. |
| Missing bar | Use the axis scale (e.g., if bars are 2, 4, 6, the missing one could be 8). |
| Relative comparison | Which bar is 1.5× another? |
2.4 Quick Strategy
- Step 1: Scan the chart for the target category or comparison.
- Step 2: Read the exact value or note the order of magnitude.
- Step 3: If a calculation is required, perform it mentally (add, subtract, multiply).
- Step 4: Verify that the answer choice matches the scale of the chart.
3. Pie Charts
3.1 Structure
| Element | What it represents |
|---|---|
| Center | Total whole (100%) |
| Slices | Proportion of the whole |
| Angles | Degrees (360° = 100%) |
| Labels | Often percentages or categories |
Key Fact:
- Angle of a slice = (percentage) × 360°.
3.2 How to Read
- Check the total – usually 360° or 100%.
- Read the label – often the percentage or category name.
- Find missing slice – subtract the sum of the given percentages from 100%.
- Convert between percentages and degrees if needed.
3.3 Common GRE Questions
| Question Type | What to compute? |
|---|---|
| Missing percentage | 100% – sum of given percentages. |
| Angle of a slice | (percentage) × 360°. |
| Comparing slices | Which slice is larger? |
| Percent of a subset | If a slice has 25% and 60% of that slice is another category, compute 0.25 × 0.60 = 0.15 → 15%. |
3.4 Quick Strategy
- Step 1: Add all given percentages.
- Step 2: Subtract from 100% to find missing slice.
- Step 3: If angles are asked, multiply the missing percentage by 360°.
- Step 4: Match the answer choice that matches the total or missing portion.
4. Worked Example 1 – Bar Chart
Problem
A bar chart shows the number of students (in hundreds) in four subjects:
| Subject | Bar height (hundreds) |
|---|---|
| Math | 6 |
| English | 4 |
| Science | 8 |
| History | 5 |
Which subject has the largest enrollment?
Solution
- Identify heights: Math = 6, English = 4, Science = 8, History = 5.
- Compare: 8 (Science) is the greatest.
- Answer: Science.
Answer Choice: C – Science (if the choices are A: Math, B: English, C: Science, D: History, E: None of