[求助]难题请教

sunandmoon

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

 

A.   the number of days with heavy rainfall was lower in 1990 than in 1910[h1] 

B.    the number of days with some rainfall, but no more than two inches, was the same in 1990 as in 1910

C.   the number of days with some rainfall, but no more than two inches, was higher in 1990 than in 1910

D.   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[h2] 

E.    the average amount of rainfall per month was lower in 1990 than in 1910

---

 [h1]ok

 [h2]

1. D1990<d1910

2. T1990>=2(t1910)

 (T1990/d1990)>2(t1910/1910)> two inches

 

johnyin

A is the only possible situation.

B and C:题目说了，小雨和中雨的天数在90年都比10年少，所以不会the same,也不会 higher than

D: interesting.  有可能虽然90年中雨天数少，但每次都取中雨最大值，即2，而虽然10年中雨天数大，但每次都取最小值，即1。  那么 90年中雨天数为n，   n*2大于2(n+1)*1么？ n为正整数，答案是一定不大于。所以也不对。

E：既然90年总降水要比10年多，平均降水怎么可能少呢？

A：注意题目问得是 possiple,not must correct.有可能大雨天数少，但每次大雨都非常大，say,100 inches.因为大雨降水量没有上限，所以可能。

[此贴子已经被作者于2008-2-13 3:18:14编辑过]

sunshoes

ls解释的好清楚啊～