310. 有一个什么gold, sliver的题。给了从同一种矿中,挖出的gold和sliver的cost分别是y 和y/2(单位好像是dollar/g).如果金、银分别sale了x?和nx? dollar,问总profit是多少。我本来觉得求利润就是找个已知条件里面的sale-cost就ok了,算完了发现答案里不单没有,还有个字母s,又回头找s到底是什么东东。。。 311. Before being simplified, the instructions for computing income tax in Country R were to add 2 percent of one’s annual income to the average of 100 units of Country R’s currency and 1percent of one’s annual income. Which of the following represents the simplified formula for computing the income tax, in country R’s currency, for a person in that country whose annual income is I? A.50+I/100。B.50+3I/100。C.50+I/40。D.100+I/50。E.100+3I/100 312. 两个长方形A、B, A长比B少10%,A宽比B多10%,问A比B面积
少1%/多1%/一样 313. 有个quadrilateral 求对角线BD (1)知道AB=5 BC=12
(2)
角A度数是其他三个角度数的平均数 314. 知道Y是constant, F(y)=KY
问F(-2)<0? (1)F(5)>0 (2)F(-3)*f(-4) >0 |