This is a classic GMAT
flaw involving percentages vs. actual values.
Here's the argument's logic:- Keating's juvenile literacy rate rose
40% over
three years.
- Nickleby's juvenile literacy rate rose only
12% over the same period.
- Conclusion: Adolescents in Keating are MORE LIKELY to become literate than those in Nickleby.
The flaw? The argument compares percentage INCREASES but draws a conclusion about overall LIKELIHOOD. These are
two very different things.
Let me show you why with numbers:
Scenario: Suppose
three years ago, Nickleby's literacy rate was
80 per
100, and Keating's was
20 per
100.
- Keating today:
20 +
40% of
20 =
28 per
100- Nickleby today:
80 +
12% of
80 =
89.6 per
100See what happened? Even though Keating's rate grew FASTER (
40% vs
12%), Nickleby's adolescents are STILL far more likely to be literate (
89.6 vs
28). The starting point — the
baseline — matters enormously.
This is exactly what Answer B identifies: without knowing what the literacy rates WERE three years ago, we cannot conclude who is more likely to be literate now.Why not C? Choice C mentions the ratio of literate to illiterate juveniles, which is essentially the same thing as the literacy rate — information we're already given in terms of percentage change. It doesn't address the missing
baseline.
Why not A or D? Population density and population growth are irrelevant because the argument is about a RATE (per
100), not total numbers.
Why not E? Spending on education might explain WHY rates changed, but the
flaw is about whether the conclusion logically follows from the data — not about causes.
Key Takeaway: Whenever a GMAT argument compares percentage changes and draws a conclusion about actual values (or likelihood), always ask: What were the STARTING points? A bigger percentage increase from a tiny base can still leave you far behind.Answer: B