請教幾道prep裡面的數學

joeywei

    

9. If x is a positive integer, is x
< 16 ?

    

(1) x is less than the average
(arithmetic mean) of the first ten positive integers.

    

(2) x is the square of an integer.

    

【B】

    

爲什麽不是E？

    

 

    

11. If p is a positive odd integer,
what is the remainder when p is divided by 4 ?

    

(1) When p is divided by 8, the
remainder is 5.

    

(2) p is the sum of the squares of two
positive integers.

    

【D】

    

爲什麽不是A？

    

 

    

 

    

18. What is the hundredths digit of
the decimal z ?

    

(1) The tenths digit of 100z is 2.

    

(2) The units digit of 1,000z is 2.

    

【E】

    

不太理解選項意思….

    

 

    

19. Is z equal to the median of the
three positive integers x, y, and z ?

    

(1) x < y + z

    

(2) y = z

    

【B】

    

爲什麽…

    

 

    

20. A certain one-day seminar
consisted of a morning session and an afternoon session. If each of the 128
people attending the seminar attended at least one of the two sessions, how
many of the people attended the morning session only?

    

(1) of the people attended both
sessions.

    

(2) of the people attended the
afternoon session. 4387

    

【B】

    

爲什麽不是C？

    

謝謝~~

kevinking08

11: p是奇数，那就是一个奇数和一个偶数的平方和。偶数的平方和能被4整除，任何一个奇数的平方和，你有没有发现，被4除都余1的。。。

18：问小数z百分位是多少，给了100倍的z的十位数（应该是个位数）和1000倍的z的个位数（应该是百位数）

19：中位数的定义是，对于奇数个数，就是中间那一个数，偶数个数，是中间两个数的算术平均。那么当y=z的时候，不论x大还是小。中位数就是y或者z了

joeywei

謝謝你呀！！