求教两道数学题

luojisi

1. 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.
A. Statement (1) alone is sufficient...........................................

2.Last year the price per share of Stock X increased by K percent and the earnings per share of Stock X increased by m percent, where K is greater than m. By what percent did the ratio of price per share to earnings per share increase, in terms of K and m?
A. k/m% B.(K-m)%  C.[100(k-m)]/(100+k)%    D.[100(k-m)]/(100+m)%   E.[100(k-m)]/(100+k+m)%

希望有会做的同学能不吝赐教

wyw1018

1. 条件1取n=2k+1  条件2 取n=3k+1 和3k+2
条件1 2取 n=6k+1和n=6k+5
2.设前年price为 P earlings 为R 根据题意 去年price为（1+k/100）*P , earlings为 (1+m/100)*R ，求{[（1+k/100）*P]/[(1+m/100)*R]-P/R}/(P/R) 解出答案为D

rainbowmanutd

第一题式E吗？我带的数。笨办法。。
第二题同意

wyw1018

第一题式E吗？我带的数。笨办法。。
第二题同意

-- by 会员 rainbowmanutd (2011/9/24 9:57:23)

应该是C，6k+1和6k+5带进去能被24整除

luojisi

答案给的是C

luojisi

请问为什么是6k+1和6k+5两种情况呢？

四夕岚

不能被2 3 同时除 综合来说不能被6除
其中当 6的余数是 234 的时候 依旧可以分别 2 3 除
所以只有余数1 5 的时候不能被2 3 分别除