Thirty years ago, the percentage of their income that single persons spent on food was twice what it is today. Given that incomes have risen over the past thirty years, we can conclude that incomes have risen at a greater rate than the price of food in that period.
Which one of the following, if assumed, helps most to justify the conclusion drawn above?
(A) The amount of food eaten per capita today is identical to the amount of food eaten per capita thirty years ago
(B) In general, single persons today eat healthier foods and eat less than their counterparts of thirty years ago.
(C) Single persons today, on average, purchase the same kinds of food items in the same quantities as they did thirty years ago.
(D) The prices of nonfood items single person purchase have risen faster than the price of food over the past thirty years.
(E) Unlike single persons, families today spend about the same percentage of their income on food as they did thirty years ago.
答案为C。该题为LSAT逻辑，出自大全。本题可用排除法用，其余4个选项都无关，全本题不知用数学公式该如何推导，请数学的NN们给推导一下啊！谢谢！
附：官方给的解释：
When arguments deal with percent/number comparisons, study scope carefully.
From the fact that single people today spend 50% less of their income on food than they did 30
years ago, and the fact that incomes rose over that period, the author draws a conclusion in the form of a
comparison: Incomes have risen faster than food prices. But this is only true if the nature and amount of
food that single people buy has stayed the same, (C). If for instance they are buying much more food now,
or caviar instead of corned beef hash, then it is quite possible that food prices have risen slower, or faster,
than incomes.
Those baffled by arguments involving economic data could have taken heart from the fact that all
four wrong choices deviate markedly from the scope. Amount of food eaten is irrelevant, which knocks out
(A) and (B); (B)’s reference to “healthier food” is even further afield. Nonfood items, (D), and food
purchased by families, (E), are in the same way not part of the author’s equations.
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发表于 2007-3-5 01:28:00
