[求助]

陈向东数学机考模拟题求解

8. The arithmetic mean of a data set is 46, and the standard deviation of the set is 4.  which value is exactly 1.5 standard deviations from the arithmetic mean of the set?

        A 42      B 44.5     C 47.5     D 50     E 52

答案是E
其实光从答案选项来看我也会选E, 因为42和50,  44.5和47.5都离46的数值是一样的.
但具体这52怎么算出来的,还请各位G友指点下,谢谢!



142. A home owner must pick between paint A, which costs $6.00 per liter, and paint B, which cost $4.50 per liter. Paint B takes one-third longer to apply than paint A. If the homeowner must pay the cost of labor at the rate of $36 per hour, which of the two paints will be cheaper to apply? 

(1)The ratio of the area covered by one liter of paint A to the area covered by paint B is 4:3. 
(2)Paint A will require 40 liters of paint and 100 hours of labor.

答案是E
但是我认为是C,  因为根据(1)和(2)的条件,就可以算出:     A的总费用=40*6+100*36.   B的总费用=40*4/3*5.4+100*4/3*36     
不知道我的思维对不对,请大家指点下!