7月29日 GMAT数学逻辑每日一练

　　7月29日 GMAT数学逻辑每日一练

　　【数学】

　　An integer greater than 1 that is not prime is calledcomposite. If the two-digit integer n isgreater than 20, is n composite?

　　(1) The tens digit of n is afactor of the units digit of n.

　　(2) The tens digit of n is 2.

　　A. Statement (1) ALONEis sufficient, but statement(2) alone is not sufficient.

　　B. Statement (2) ALONEis sufficient, but statement(1) alone is not sufficient.

　　C. BOTH statements TOGETHERare sufficient,but NEITHERstatement ALONEis sufficient.

　　D. EACHstatement ALONEis sufficient.

　　E. Statements (1) and (2) TOGETHERare NOTsufficient.

　　【逻辑】

　　The mind and the immune system have been shown to beintimately linked, and scientists are consistently finding that doing gooddeeds benefits one’s immune system. The bone marrow and spleen, which producethe white blood cells needed to fight infection, are both connected by neuralpathways to the brain. Recent research as shown that they activity of thesewhite blood cells is stimulated by beneficial chemicals produced by the brainas a result of magnanimous behavior.

　　The statements above, if true, support the view that

　　A. good deeds mustbe based on unselfish motives lack of magnanimity is the cause of most seriousillnesses.

　　B. magnanimousbehavior can be regulated by the presence of absence of certain chemicals inthe brain.

　　C. magnanimousbehavior can be regulated by the presence or absence of certain chemicals inthe brain.

　　D. magnanimity isbeneficial to one’s own interests

　　E. the number ofwhite blood cells will increase radically if behavior is consistentlymagnanimous

　　答案

　　【数学】

　　参考答案：A

　　题目翻译：比1大的非质数整数叫合数，那么大于20的整数是不是合数？

　　题目全解：

　　(1) The tens digit of n is a factor of the units digit of n.

　　If this is true then n is NOT a prime number. This is true because if the tens digit is a factor of the units digit, the whole number will be divisible by that number because the tens digit is obviously a factor of itself! Try it out:

　　2X = 22, 24, 26, 28

　　3X = 33, 36, 39

　　4X = 44, 48

　　5X = 55

　　6X = 66

　　7X = 77

　　8X = 88

　　9X = 99

　　For each of these numbers the tens digit evenly goes into itself and is then a factor of the units. Impossible to have a prime number under these rules. SUFFICIENT

　　(2) Statement 2 tells us nothing on its own. n could be prime (23) or composite (24)

　　【逻辑】

　　参考答案

　　思路：In my view, the reasoning in this argument is that:

　　magnanimous behavior beneficial chemicals produced by thebrain they activity of these white blood cells fight infection

　　So, the correct answer is D.

　　A is out of scope. Because unselfish motives is notmentioned in this argument.

　　B and C have the same mistake. From the above reasoning , itis clear that because of magnanimous behavior, some beneficial chemicals wereproduced by the brain. But the statement of B and C fail to convince us thatmagnanimous behavior can be regulated by the presence of absence of certainchemicals in the brain.

　　E is out of scope. The argument fails to establish thecasual relationship between the number of white blood and the rate ofmagnanimous behavior.

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