数学学渣求数学大神帮忙。祝好运！

flpalmbeach

The main ingredient in a certain prescription drug capsule costs $500.00 per kilogram.  If each capsule contains 600 milligrams of the ingredient, what is the cost of the ingredient in a capsule? (1 kilogram = 10^6 milligrams)

(A) $0.30

(B) $0.83

(C) $1.20

(D)$3.00

(E) $3.33

这题选B。 可我怎么都算不出来。

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 (arithmetic mean) of 100 units of Country R's currency and 1 percent 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/200)

(B) 50+(3I/100)

(C) 50+(I/40)

(D) 100+(I/50)

(E) 100+(3I/100)

这题选C  可是怎么列试子呢？

If $1,000 is deposited in a certain bank account and remains in the account along with any accumulated interest, the dollar amount of interest, I , earned by the deposit in the first n years is given by the formula I=1000〔(1 + r/100)^n --1〕, where r percent is the annual interest rate paid by the bank.  Is the annual interest rate paid by the bank greater than 8 percent?

(1)  The deposit earns a total of $210 in interest in the first two years.

(2)  (1+r/100)^2>1.15

这题选A。  可是条件二单独为什么不充分呢？

If x, y, and z are integers and xy + z is an odd integer, is x an even integer?

(1) xy + xz is an even integer.

(2) y + xz is an odd integer.

这题选A  为什么呢

非常感谢！！！！！！！

yuning31

第一題的答案是不是有錯啊><?

第二題題目非常繞，讀好久，但讀懂後不難
某人的income是I，income tax的算法是2%的income加上100和1%income的平均：
income: I
2% of one's income: 2I/100
average of 100 units and 1% of one's income: (100+1I/100)/2 = 50+I/200

2I/100+50+I/200 = 5I/200+50 = I/40+50

第三題的二選項我帶數字進去發現如果是8%會等於1.16.....>1.15但7.9%也是等於1.16.....還是>1.15

第四題分別把x, y, z的奇偶性用表格列出來，會發現當y是奇數時，x可以是奇也可以是偶

flpalmbeach

yuning31 发表于 2017-10-26 13:49
第一題的答案是不是有錯啊>

谢谢你哦。 我觉得第一题答案也可能错。我选了A。 祝你好运。