Tables & Data Sets
1. Core Idea
A table gives you exact values rather than a picture, so there is no estimation error — but also no visual shortcut. Everything must be read carefully.
The efficiency skill is selective reading: never read the whole table. Locate the row and column the question needs, extract those numbers, and stop.
2. Must-Know Rules
Before the questions, spend 30 seconds on:
- Row labels — what does each row represent?
- Column headers — what does each column measure?
- Units — check every column separately; they often differ.
- Totals row/column — is one provided, or must you compute it?
- Footnotes — often define a term or flag an exception.
The recurring calculations:
| Question | Method |
|---|---|
| Row total | sum across the row |
| Column total | sum down the column |
| Percent of total | cell / relevant total |
| Percent change across columns | (later - earlier)/earlier |
| Ratio between two cells | divide |
| Average of a row | row total / number of entries |
| Which is greatest | scan, shortlist, then compute |
Cross-referencing. Many table questions need two cells from different rows and columns. Point to both with two fingers (or note them down) before computing — this prevents the classic "read the wrong row" error.
3. Worked Examples
Example 1 — Percent of a row total
A table shows Q1 sales by region: North 120, South 180, East 90, West 210 (in thousands). What percent of total sales came from the South?
Total = 120 + 180 + 90 + 210 = 600.
South share = 180/600 = 30%.
Example 2 — Percent change across columns
A table shows a product's units sold: 2022 = 4,500; 2023 = 5,400. What is the percent change?
(5400 - 4500)/4500 = 900/4500 = 0.20 = 20% increase.
Example 3 — Ratio across rows
Employees: Department A has 45 staff with a total payroll of $2,700,000. Department B has 30 staff with a total payroll of $2,100,000. Which has the higher average salary, and by how much?
A: 2,700,000/45 = $60,000.
B: 2,100,000/30 = $70,000.
B is higher, by $10,000.
4. GRE Traps
- Reading the adjacent row or column. The most common careless error under time pressure.
- Mixed units across columns. One column in thousands, another in units — always check each header.
- Using the grand total when a row total is needed (or vice versa).
- Assuming the columns sum to the total row. Sometimes a table includes an "Other" category excluded from the listed rows; footnotes will say.
- Ignoring a footnote. They are there for a reason and usually matter for at least one question.
- Computing more than needed. If the question asks only about two rows, don't total the table.
- Percent change base. Always the earlier value.
5. Speed Tricks
- Locate before you calculate. Find both cells, write them down, then compute.
- Compute a total once if several questions in the set need it, and reuse.
- Estimate to shortlist on "which is greatest" questions — compute only the top two.
- For per-unit comparisons (average salary, cost per item), divide the totals rather than working with individual entries.
- Use the calculator only for genuinely awkward division — 180/600 is a mental step.
- Rewrite awkward numbers as fractions: 180/600 = 3/10 = 30%, faster than long division.
6. Self-Check
Q1. A table shows costs: 240, 360, 200, 400. What percent of the total is the second value?
Q2. A value goes from 250 in 2023 to 200 in 2024. What is the percent change?
Q3. Team A: 8 members, 640 total points. Team B: 5 members, 425 total points. Which has the higher average?
Answers
A1. Total = 1,200. 360/1200 = 30%.
A2. (200 - 250)/250 = -0.20 = a 20% decrease.
A3. A: 80. B: 85. Team B.
7. One-Line Summary for the Board
Read the headers and units first. Locate the exact cells, then compute — never total the whole table.