数学JJ第100题+PREP 2 道 提问！！请进！！！！

at least 的意思是>=100, F=400 ,无法比较

JJ：
有三项活动，S,C,A，参加C的都参加A，参加S和A的有9人。参加C的有16人。三项都参加的有4人。问参加了两项的人数。
我对参加S和A的9个人，这个信息理解有歧义。按照答案的17，三项都参加的4个人是包含在这9个人里面的。可是按照题目的意思，可不可以理解成这9个人就是参加2项的，还有另外4个人参加三项？这样的话，答案就应该是21了。
我理解的有错吗？如果有错，为什么不能这么理解呢？
你的理解没有错，到时候看题目是怎么问的吧。如果是至少参加S和A，那就是17；如果是只参加S和A那就是21.

PREP：
1、Before being simplifed, the instructions for computing income tax in Country R were to ass 2 percent of one's annual income to the average (arithmetic mean) of 100 units of Country R's currency and 1 percent of one's annual income. Which of the following represents the simplied fomula for computing the income tax, in Country R's currency, for a person in that country whose annual income is I?
答案：50+I/40

不好意思，我没有看懂“ ass 2 percent of one's annual income to the average (arithmetic mean) of 100 units of Country R's currency and 1 percent of one's annual income”？

PREP：
1、Before being simplifed, the instructions for computing income tax in Country R were to add 2 percent of one's annual income to the average (arithmetic mean) of 100 units of Country R's currency and 1 percent of one's annual income. Which of the following represents the simplied fomula for computing the income tax, in Country R's currency, for a person in that country whose annual income is I?

答案：50+I/40

2% * I + average(100 + I *%)  = 2.5%*I + 50

题目错了，应该是"add 2 percent of one’s annual income to the average (arithmetic mean) of 100 units of country R’s currency and 1 percent of one’s annual income"。

So, 式子可立为： 2%I+（100+1%I）/2 = 50+0.025I=50+I/40