6.5 Following Quantitative Concepts in Reading Comprehension Passages
Key Takeaways
- GMAC says Reading Comprehension measures the ability to follow the development of quantitative concepts presented in written material, alongside its six named reading skills.
- Verbal passages express quantities in words, so label what each figure describes: a total, a rate, a share, a percentage change, or an average.
- A percentage change and a percentage-point change differ: a share rising from 10% to 12% is a 2-point increase but a 20% relative increase.
- Rates, shares, and averages can move differently from totals, so a falling rate does not prove a falling count unless the base stayed the same.
- Quantitative Reading Comprehension questions usually ask what a comparison or trend implies, so translate numbers into relationships before reading the choices.
Why Quantitative Concepts Appear in Verbal Reasoning
GMAC's Exam Content page says Reading Comprehension questions measure your ability to "follow the development of quantitative concepts" in written material. You will not solve equations in Verbal Reasoning, but business, economics, and science passages regularly describe growth rates, market shares, averages, and statistical findings in words. The questions test whether you understand what those quantities mean and what they do not prove.
Translate Every Number Into Its Role
When a passage mentions a figure, label what kind of quantity it is before moving on:
| Quantity Type | Example Phrase | What It Does Not Tell You |
|---|---|---|
| Total (count) | "The firm sold 40,000 units" | Whether sales were high relative to the market |
| Rate or ratio | "Defects per 1,000 units fell" | Whether the total number of defects fell |
| Share (proportion) | "Online orders rose to 30% of sales" | Whether online orders grew in absolute terms |
| Percentage change | "Revenue grew 8%" | How large the starting base was |
| Percentage-point change | "Market share rose 2 points, from 10% to 12%" | That the same move is a 20% relative increase |
| Average | "Average wait time dropped to 6 minutes" | How many people waited, or whether the longest waits shrank |
Five Relationships to Track
- Rate versus total: A lower accident rate is compatible with more accidents if traffic grew. A total equals the rate times the base, so you need both before comparing totals.
- Share versus amount: A product's share of sales can fall while its sales rise, if the whole market grows faster.
- Percent versus percentage points: Moving from 10% to 12% is a 2-percentage-point increase and a 20% relative increase. Answer choices exploit the difference.
- Average versus distribution: A higher average income is compatible with most people earning less, if a few earners gained a great deal.
- Association versus size of effect: "Regions with more clinics have lower mortality" does not say how much of the difference, if any, the clinics cause.
Worked Example
Practice passage excerpt written for this guide: "Between 2015 and 2020, the share of Lakeland's electricity generated from wind rose from 12 percent to 18 percent. Over the same period, total electricity generation in Lakeland fell by 10 percent as factories closed. Some commentators concluded that the amount of wind power generated in Lakeland rose by half."
Work it through with an index. If total generation was 100 units in 2015, wind produced 12 units. In 2020, total generation was 90 units, and wind's 18 percent share of that total is 16.2 units. Wind output therefore rose by 4.2 units, or 35 percent, not by half. The commentators treated the rise in share (from 12 to 18 percent, a 50 percent relative increase) as if it were a rise in the amount of wind power, ignoring the shrinking total.
A question might ask why the commentators' conclusion is flawed. The correct choice would describe confusing a change in proportion with a change in amount, or overlooking the decline in total generation. A tempting wrong choice would claim that wind output fell, which the figures contradict.
A Second Example: Rates and Totals
Practice passage excerpt written for this guide: "After Harbor County lowered its speed limits, its rate of traffic fatalities per 100 million vehicle-miles fell by 20 percent. Over the same period, the total number of traffic fatalities in the county stayed the same."
These two facts fit together only if total driving rose. Suppose the earlier rate was 1 fatality per 100 million vehicle-miles and drivers covered 100 million miles, for 1 fatality. The new rate is 0.8, and fatalities stayed at 1, so driving must have risen to 1 ÷ 0.8 = 1.25, or 125 million vehicle-miles, a 25 percent increase. An inference question would reward "total vehicle-miles traveled in the county increased." A trap choice would claim that the lower limits did not make driving safer per mile, which contradicts the falling rate.
Reading Trends and Comparisons in Prose
- Direction words: "Increased," "declined," "leveled off," and "reversed" describe change; note the starting and ending points and whether the change is absolute or relative.
- Comparative wording: "Twice as likely" compares probabilities, not counts, and "grew faster" compares growth rates, not sizes.
- Scope of the data: A figure about "surveyed managers" or "the northern plants" does not automatically describe all managers or all plants.
Traps in Quantitative Answer Choices
| Trap | What the Choice Does | Quick Check |
|---|---|---|
| Rate-total swap | Treats a change in a rate as a change in a count | Did the base stay the same? |
| Share-amount swap | Treats a change in share as a change in amount | Did the whole grow or shrink? |
| Point-percent swap | Confuses percentage points with percent change | Subtract, then divide by the starting value |
| Average overreach | Draws conclusions about most individuals from an average | Could a few extreme values explain the average? |
| Unsupported precision | States an exact figure the passage never provides | Can you compute it from the passage alone? |
A passage states: 'In 2019, 20 percent of Company Q's revenue came from services. By 2023, services accounted for 25 percent of the company's revenue, even though the company's total revenue had declined by 20 percent over that period.' Which of the following can be properly inferred from the passage?
A passage on public health states: 'After a city added protected bike lanes, the number of cycling injuries reported each year rose by 15 percent. Traffic counts, however, showed that the number of cycling trips in the city had doubled over the same period.' Which of the following conclusions is most strongly supported by the passage?
A passage states: 'In a survey of 2,000 employees, the average number of hours worked per week rose from 42 to 45 after the company introduced flexible scheduling. A manager concluded that most employees began working longer weeks.' Which of the following, if true, would most seriously undermine the manager's conclusion while remaining consistent with the survey result?