求救 GWD-29-35

我要飞

In Patton City, days are categorized as having heavy rainfall (more than two inches), moderate rainfall (more than one inch, but no more than two inches), light rainfall (at least a trace, but no more than one inch), or no rainfall.  In 1990, there were fewer days with light rainfall than in 1910 and fewer with moderate rainfall, yet total rainfall for the year was 20 percent higher in 1990 than in 1910.

 

If the statements above are true, then it is also possible that in Patton
                    City

 

1. the number of days with heavy rainfall was lower in 1990 than in 1910
2. the number of days with some rainfall, but no more than two inches, was the same in 1990 as in 1910
3. the number of days with some rainfall, but no more than two inches, was higher in 1990 than in 1910
4. the total number of inches of rain that fell on days with moderate rainfall in 1990 was more than twice what it had been in 1910
5. the average amount of rainfall per month was lower in 1990 than in 1910

A  

我的问题比较多啊？我怎么怎么推都推不出来呢？

HR(more than two inches)   MR(more than one inch, but no more than two inches) LR(at least a trace, but no more than one inch) NR

                          1990                           1910

                        D(MR)         <              D(MR)

                        D(LR)         <              D(LR)

                      TOTAL R      >           TOTAL R

那怎么说也是HR在90年的日子多呀，怎么会选A 呢？我觉得E比较又可能，就是大雨集中在少数天，但是总量很大，导致每个月的平均降雨量很小。

这样分析对吗？请指正！

stavan

这个题目回答过很多次了..翻出个链接...楼主自己看看吧..

http://forum.chasedream.com/dispbbs.asp?BoardID=24&replyID=2968343&id=329449&skin=0

我要飞

非常感谢！！！

Howto

其实这题蛮简单的，我来写

就根据楼主写的那个A说 HR的天数 1990 和1910 我们先不知道

B说 小于2inch的降雨量的天数 1990 和1910 一样。根据题目我们知道小于2inch 降雨量的是 LR 和MR， 我们又知道 LR和MR在1990都小于

1910. 所以LR+MR 也是1990 小于1910. 所以Ｂ和C都错

D说在MR天下的雨量 1990是1910的两倍。我们知道在MR天数下的雨量=天数 * 平均每天的降雨量。 我们还知道 MR天在1990少，而且ＭＲ天降

雨是　大于等于１　小于２的。所以取极限 就算降雨的天数是一样的，除非MR降雨量可以=2 才可能使得1990是1910 的两倍。

E说月平均降雨量1990小于1910。 我们知道总的降雨量是1990>1910的 那么两边都除以12，就是月平均降雨量。还是1990大于1910.所以E也

错。

最后看A为什么对呢。问题问的是possible成立. A说1990 下HR 的天数比1910少。这个是可以成立的因为下HR的时候雨量是没有上限的， 比如

1990只下了一天的ＨＲ但是雨量是１００.　而１９１０下了１０天的HR 雨量每次都是3. 这样不会违背上面的任何一个条件。

我要飞

太谢谢了，请问您复习多久了？怎么复习的？我好想碰到一个很长的瓶颈期了，特别的受打击，正确率就维持在70%左右。。。我很急，也很慌，能给些建议吗？