数学prep题求教

看似不难得，可是都做不对哦。。。帮偶看一下

(1) what is the result when x is rounded to the nearest hundredth?

(1) when x is rounded to the nearest thousandth, the result is 0.455

(2) The thousandth digit of x is 5

answer:C, Mine:A题目的意思是不是x的百分位多少？那么千分位知道了，不是百分位就可以知道么？我的想法不对？

If n is a positive integer and r is the remainder when (n-1)(n+1) is divided by 24, what is the value of r?

(1) 2 is not a factor of n

(2) 3 is not a factor of n

answer:C, mine: E这题怎么思考亚？

(3) A certain meter records voltage between 0 volts and 10 volts, inclusive. If the average (arithmetic mean) value of 3 recordings on the meter was 8 volts, what was the smallest possible recording, in volts?

answer:4, 怎么不是6?

thanks

回答你的第一个问题，条件1的意思是四舍五入到千分位后为0.455，原来的数可能是0.4551-0.4554，也可能是0.4546-0.4549。因此，条件1单独无法确定