Explanation
Reading the question: this prompt is not quite like any
we've seen so far, in that it presents statistics and no argument. This setup
is perfect for proof by stronger terms: the conclusion that is "most properly
drawn" will be one that must be
drawn--in other words, the answer choice that must be true. We can head straight to the answer choices to
establish that proof.
Logical proof: first, must (A) be true? No; we are given
only percentages, not numbers, and we have no way of inferring numbers. We
could have a case in which Paisi's population is
very, very small. So (A) is out. Must choice (B) be true? No; these two
countries are mentioned in different facts that remain unconnected. It could be
that Paisi is very, very small and Kappa is very,
very big. Skipping (C) for a moment, we can quickly knock out (D) and (E) also
by analysis by cases: we can imagine different cases for countries that haven't
been mentioned, or years that haven't been mentioned, and that data could
diverge wildly or not at all and still leave the above true.
We're left with (C). Must (C) be true? In the prompt, we
have that 20% more people smoke than 20 years ago. Also, the first sentence
says that the rate is higher than ever before. Combining them, say the
population 20 years ago was 100, and x% of them smoked, which is 100x people. Today, the number of people
that smoke is 1.2(100x). But the rate of smoking now is x or
greater ("higher than ever before"), meaning that 1.2(100x) divided by
the current population is greater than or equal to x:
Multiplying both sides by P and dividing both sides by x,
we have:
Indeed, today's population P can be no greater than the
population of 20 years ago, which we had picked to be 100 but could have left as
a variable. Here we used a technique that is common in GMAT Problem Solving: when working with percentages, try assuming
a total value of 100 to make your line of reasoning more concrete. The
correct answer is (C).
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