106. 11122-!-item-!-187;#058&007588
If a certain sample of data has a mean of 20.0 and a standard deviation of 3.0, which of the following values is more than
2.5 standard deviations from the mean?
(A) 12.0
(B) 13.5
(C) 17.0
(D) 23.5
(E) 26.5
<A>
142. 14580-!-item-!-187;#058&010013
The rate of a certain chemical reaction is directly proportional to the square of the concentration of chemical A present and inversely proportional to the concentration of chemical B present. If the concentration of chemical B is increased by 100 percent, which of the following is closest to the percent change in the concentration of chemical A required to keep the reaction rate unchanged?
(A) 100% decrease
(B) 50% decrease
(C) 40% decrease
(D) 40% increase
(E) 50% increase
<D>
怎麼算都怪怪的
106，20-3*2.5=12.5
20+3*2.5=27.5
A不在这个范围内。
142，是怪怪的~
设这个rate为x，A^2为10，B为10，那么x：A^2=1：10；x*B=10.
现在B变为20，x就变为0.5，A^2变为5.
为了让x回到1，A^2必须回到10，那么A^2要增长100%，A要增长30+%，所以选D。
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