问几道prep2的题

renyouyang

谢谢楼上滴~

perpetuo

第一题我真的没看明白，不过第二题我有点想法

t除以7余6，那么5t除以7肯定余2，对吧，

t2除以7余1，这是已知

还有个常数6，6除以7还是余6，

所以三个加起来，是2+1+6=9

那么9-7=2，所以应该是可以的...

如果我说的有问题请大家多指出来...

renyouyang

几道prep不太懂，希望会做的战友给我讲一点点。。。

70, 75, 80, 85, 90, 105, 105, 130, 130, 130
The list shown consists of the times, in seconds, that it took each of 10 schoolchildren to run a distance of 400 meters.  If the standard deviation of the 10 running times is 22.4 seconds, rounded to the nearest tenth of a second, how many of the 10 running times are more than 1 standard deviation below the mean of the 10 running times?
(A) One
(B) Two
(C) Three
(D) Four
(E) Five
KEY:B
不知道题目什么意思耶。。。

If t is a positive integer and r is the remainder when t^2 + 5t + 6 is divided by 7, what is the value of r ?
(1) When t is divided by 7, the remainder is 6.
(2) When t^2 is divided by 7, the remainder is 1.
A
1会，2不会

Does the integer k have a factor p such that 1 < p < k ?
(1) k > 4!
(2) 13! + 2=<k=<13! + 13
B
依然1会，2不会

Set S consists of five consecutive integers, and set T consists of seven consecutive integers.  Is the median of the numbers in set S equal to the median of the numbers in set T ?
(1)  The median of the numbers in set S is 0.
(2)  The sum of the numbers in set S is equal to the sum of the numbers in set T.
C
觉得这道题一定很简单，但是我脑子荡到了，会选B，举不出列子来推翻2

[此贴子已经被作者于2008-9-17 22:52:11编辑过]