求助一道GWD逻辑题

rainny0906

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

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

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

答案是A,为什么？

nileshu

因为1990年的heavy rain day 可以是极端值，一天（更加极端情况下）或几天下掉1910年的下雨量。

sdcar2010

If all the heavy rainfall days in 1990 had 100 inches of rain and all the heavy rainfall days in 1910 had no more than 3 inches . . .

A is correct

There are only two likely possibilities for 1990 to have more total rainfalls than 1910:

1) Total rainfalls from heavy rainfalls is bigger in 1990 than in 1910.  This could be done either by very heavy rains in a few days in 1990 or with more heavy rainfalls days in 1990
2) Total rainfalls from moderate/light rainfalls is bigger in 1990 than in 1910.  This possibility sounds counterintuitive but is mathmatically possible.  Keep in mind the definition of moderate/light rainfalls is based on a range. It is conceivable that a moderate rainfalls day could have either 1.9 inch or 1.1 inch of rain.  So if all the moderate rainfall days in 1990 had 1.9 inch while all the moderate rainfall days in 1910 had only 1.1 inch, the total rainfall in 1990 could be bigger than in 1910.

Answer A points out the first possibility and is the right answer.

rainny0906

明白了，多谢

barbaradu

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