急问PREP数学题~求NN解答！

sarah_kim

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

------------------------------------------------------------------------------------------------------------------------------------

【答案】A

62.7564-!-item-!-187;#058&005577

Alice
's take-home pay last year was the same each month, and she saved the same fraction of her take-home pay each month.The total amount of money that she had saved at the end of the year was 3 times the amount of that portion of her monthly take-home pay that she did not save.If all the money that she saved last year was from her take-home pay, what fraction of her take-home pay did she save each month?


(A) 1/2

(B) 1/3

(C) 1/4

(D) 1/5

(E) 1/6

没看懂具体意思。。


多谢了！！

sarah_kim

为什么要*3呢？？

sarah_kim

谢谢！！！！也谢谢LS哈