Data Interpretation
Data Interpretation is the one place on the GRE where several questions hang off a single figure — a table, a pair of graphs, or a pie chart — so a few minutes spent reading the display carefully pays off across two or three questions. The maths itself is deliberately gentle: percentages, ratios, averages and simple differences. The difficulty is entirely in the reading — which row, which axis, which whole, which units, and whether the question wants an exact value or an estimate. The GRE rewards test-takers who orient to a chart before touching a number: read the title, the axis labels and the footnotes first. This chapter drills the four display types the GRE reuses — tables, bar and line graphs, pie/circle graphs, and multi-source sets — and the estimation habits that let you skip the slow on-screen calculator whenever the answer choices are far apart.
Topics
⚡ GRE shortcuts & speed methods
The fastest ways to crack this chapter under time pressure — the techniques that separate a 95+ percentiler from the rest.
- Orient before you compute: read the title, axis labels, legend and units first — most DI errors are reading errors, not arithmetic.
- Compute the grand total once, write it down, and reuse it across every linked question in the set.
- If the answer choices are far apart, round hard and estimate — the on-screen basic calculator is slow; save it for close choices.
- Convert a pie slice to a real value in one step: (slice percent) × grand total. Angle to percent: (angle/360) × 100.
- On a line graph, the steepest segment is the greatest rate of change — you rarely need to read exact values to find it.
- For "percent of total" always anchor to the grand total, never a row or column subtotal.
- Never compare slices across two pies without first converting each to an absolute number using its own total.
⚠️ Common mistakes & traps
GRE is designed so that careless errors here cost you marks. Internalise each trap before the exam.
- Ignoring "in thousands / millions" and reporting a raw table figure that is off by a factor of 1,000.
- Taking a percent of the wrong whole — a category subtotal instead of the grand total.
- Reading a truncated axis (starting above zero) as if bar differences were proportional to their heights.
- Comparing pie slices across two charts by percent when the two totals differ.
- Reading a stacked bar’s cumulative top as a single segment instead of subtracting the lower segment.
- Computing extra values the question never asked for — multi-source sets bait you with irrelevant data.
📈 GRE exam insight & question patterns
Quantitative Comparison — a pie shows Dept X at 20% of a 6,000-person firm; another firm’s Dept X is 30% of 3,000 people. Quantity A: heads in the first. Quantity B: heads in the second. Which is greater?
A = 0.20 × 6000 = 1200; B = 0.30 × 3000 = 900. Quantity A is greater. Convert percents to counts before comparing.
How are GRE Data Interpretation questions bundled?
In a set of 2–3 questions that all reference the same figure(s). Read the display thoroughly once; it pays back across every question.
A DI question gives choices of 12%, 20%, 33% and 50% for a percent increase from 250 to 300. How should you work?
The choices are far apart, so estimate: 50/250 = 1/5 = 20%. No calculator needed.
Numeric Entry — a 25% pie slice equals 150 units. Enter the grand total.
150 is one quarter of the total, so the total is 150 × 4 = 600.
🎴 Flashcards — instant recall
Tap a card to reveal the answer. Drill these until they are automatic.
📌 Quick revision
- Data Interpretation bundles 2–3 questions on one figure; the maths is easy, the reading is where points are won or lost.
- Always read the title, axis labels, legend and units before computing — and watch for "in thousands / millions".
- Anchor every "percent of total" to the grand total, and compute that total once to reuse across the set.
- Turn a pie slice into a value with (slice percent) × grand total; convert angles via (angle/360) × 100.
- On line graphs the slope is the story: the steepest segment marks the fastest change.
- Never compare slices across two pies by percent alone — convert each to an absolute count first.
- Estimate boldly when answer choices are far apart; reserve the slow on-screen calculator for close calls.
Chapter test
🏆 Vidaara GRE success checklist
You have truly mastered Data Interpretation when you can tick every box below.
- Recall every formula in this chapter without looking them up
- Solve each topic’s practice set with at least 80% accuracy
- Use the chapter shortcuts to cut your solving time in half
- Spot and avoid every common trap listed above
- Score 80%+ on the timed chapter test
📋 Chapter mastery scorecard
Track where you stand. Aim for the target before moving to the next chapter.
| Skill checkpoint | Target |
|---|---|
| Concept theory & formulas understood | 100% |
| Topic practice sets attempted (4 topics) | 4/4 |
| Best topic-test score | — → 80%+ |
| Chapter test score | — → 80%+ |
| Flashcards drilled to instant recall | 7 cards |
Formula Reference Sheet
The workhorse relationships
| Percent of a total | (part / total) × 100 % |
|---|---|
| Percent change | (new − old) / old × 100 % |
| Value from a pie slice | (slice percent) × grand total |
| Slice angle ↔ percent | percent = (angle / 360°) × 100 |
Reading & estimating
| Average of several bars | (sum of the bar heights) / (number of bars) |
|---|---|
| Ratio of two categories | value A : value B (same units!) |
| Estimation cue | if the answer choices are far apart, round and skip the calculator |