求助PREP2的几道题

chipmunk

1If x and y are positive integers, is xy a multiple of 8 ?
(1) The greatest common divisor of x and y is 10.
(2) The least common multiple of x and y is 100.
2Store S sold a total of 90 copies of a certain book during the seven days of last week, and it sold different numbers of copies
on any two of the days. If for the seven days Store S sold the greatest number of copies on Saturday and the second
greatest number of copies on Friday, did Store S sell more than 11 copies on Friday?
(1) Last week Store S sold 8 copies of the book on Thursday.
(2) Last week Store S sold 38 copies of the book on Saturday
3Is the integer n odd?
(1) n is divisible by 3.
(2) 2n is divisible by twice as many positive integers as n.
414393-!-item-!-187;#058&010357
x, 3, 1, 12, 8
If x is an integer, is the median of the 5 numbers shown greater than the average (arithmetic mean) of the 5 numbers?
(1) x > 6
(2) x is greater than the median of the 5 numbers.
4A manufacturer produced x percent more video cameras in 1994 than in 1993 and y percent more video cameras in 1995
than in 1994. If the manufacturer produced 1,000 video cameras in 1993, how many video cameras did the manufacturer
produce in 1995 ?
(1) xy = 20
(2) x + y + 100
xy
= 9.2

Wangycbest

第1题
xy=最大公约数*最小公倍数, 所以选C

Wangycbest

最后一题 我也错了. 后来重做了一下, 选B
1995年产量=1994年产量*(1+y/100)=1993年产量*(1+x/100)*(1+y/100)=1000*(1+x/100+y/100+xy/10000)=1000+10(x+y+xy/100)
把(2)代进去就算出来了

mop000

Is the integer n odd?(1)n is divisible by 3(2)2n is divisible by twice as many as positive integers as n1)不一定，比如6 (2)n一定是奇数。如果n是奇数，那么2n的因子的数量是 n的因子的数量 的2倍。如果是偶数，则不然。 证明不写了，给你举个例子 比如 n=21 它的因子为 1，3，7，21，总共4个 2n的因子为 1，2，3，6，7，14，21，42，总共8个 再比如 n=6 它的因子为 1，2，3，6，总共4个 2n的因子为 1，2，3，4，6，12，总共6个网上看到的

windows10

第2题卖书的. 我还没有PREP到,正确答案是B 吗?
(1)不充分. 简单代数字进去, 周五卖10本或者12本都可以
(2)充分.  
假设周五卖11本, 那么除了周五周六以外的五天总共要卖41本。但因为每天卖

的数量不同而且这5天里的某一天最多只能卖10本，五天最多卖

10+9+8+7+6=40<41本。因此周五卖的数量要大于11本。

windows10

那道MEDIAN的题，我也没有PREP到，正确答案是E?
1）不充分。
x>6, 那么median可能是x(当x=7时). 7>31/5, 所以median>mean
median也可能是8 (当x>8). mean=(24+x)/5>32/5, median=8, 不确定哪个大.
2) 不充分.
x>median , 即x>8, median=8, mean=(24+x)/5>32/5, 不确定哪个大.

2)的条件包含了1)的条件,所以和起来也不能确定哪个大.