请教几道GMATPrep的数学题

AthosJingle

1. Before being simplified, the instructions for computing income tax in Country R were to add 2 percent of one's annual income to the avergage (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 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

我列的式子是

I*2%+mean(100+I*1%)

然后就算不下去了，随便懵了一个E。请问应该怎么做呢？谢谢！

2. Of the 60 animals on a certain farm, 2/3 are either pigs or cows. How many of the animals are cows?
(1) The farm has more than twice as many cows as it has pigs.
(2) The farm has more than 12 pigs.

我的算法是

c+p=60*2/3=40

(1) p>2c

(2) p>12

这样算出来是E，但是答案居然是C？

[此贴子已经被作者于2008-1-14 22:32:36编辑过]

monacopig

I*2%+(I*1%+100)/2= 50+I/40

monacopig

pig=p, cow=c
p+c=40, 问 c=?
(1)=>p>2c
(2)=>c>12

only when c=13, p=27, then p+c=40

if c>13, for example, if c=14, p>28, then p+c>40

So, only one posibility, that is c=13, p=27, choose C

AthosJingle

多谢monacopig。

第一题明白了，自己想得太复杂，以为是全国民的100+I*1%的平均。

Q 2,

(2) The farm has more than 12 pigs.

(2) => p>12, not c>12!

难道题目错了？

monacopig

Sorry, my bad
(1) => c>2p (pay attention to this)
(2) => p>12

AthosJingle

要命，这一句完全被绕晕了，明白了，多谢！

boston8899

c+p=40

1.c>2p

2.p>12

then p can only be 13,