急！！几道简单的数学题，求高人指点~~~

sby188 · 发表于 2011-5-17 10:09:28

1 How many liters of apple juice were added to the cranberry juice in a certain container?
(1) The amount of apple juice that was added was 3/2 the amount of cranberry juice in the container.
(2) There were 5 liters of cranberry juice in the container.

Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.

正解是 C

2 In a demographic study, the population and total income of a certain region were estimated from other data, and both estimates had lower and upper limits. At the time of the estimates, was the per capita income for the region greater than $16,500?
(1) The lower limit for the estimate of the population was 330,000 people.
(2) The lower limit for the estimate of the total income was $5,500,000,000.

Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient

正解是E

3 Is |x |?< 1?
(1) |x + 1|? = 2|x - 1|
(2) |x - 3| ≠ 0

Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.

正解是 C

4 Six cards numbered from 1 to 6 are placed in an empty bowl. First one card is drawn and then put back into the bowl; then a second card is drawn. If the cards are drawn at random and if the sum of the numbers on the cards is 8, what is the probability that one of the two cards drawn is numbered 5 ?

答案是 2/5

5 The function f is defined by f(x) = √x – 10 for all positive numbers x. If u = f(t) for some positive numbers t and u. What is t in terms of u?

答案是 (u + 10)^2

夜夜箫歌 · 发表于 2011-5-17 10:39:09

Six cards numbered from 1 to 6 are placed in an empty bowl. First one card is drawn and then put back into the bowl; then a second card is drawn. If the cards are drawn at random and if the sum of the numbers on the cards is 8, what is the probability that one of the two cards drawn is numbered 5 ?
和为8的组合有（2,6）（3,5）（4,4）（6,2）（5,3），一共五种，其中有5的有两种，所以是2/5

夜夜箫歌 · 发表于 2011-5-17 10:41:25

The function f is defined by f(x) = √x – 10 for all positive numbers x. If u = f(t) for some positive numbers t and u. What is t in terms of u?

这个函数是根号x减去10吗，根号断了。。
如果是根号X减去10的话，因为f（t)=根号t-10=u
所以t=（u+10）^2

夜夜箫歌 · 发表于 2011-5-17 10:45:20

How many liters of apple juice were added to the cranberry juice in a certain container?
(1) The amount of apple juice that was added was 3/2 the amount of cranberry juice in the container.
(2) There were 5 liters of cranberry juice in the container.
第二个条件单独显然不能求得答案，第一个条件，假设the amount of cranberry juice=x，则The amount of apple juice=3/2*x，条件不充足无法求出X
两个条件一起的话，因为the amount of cranberry juice=5，所以The amount of apple juice=3/2*5

夜夜箫歌 · 发表于 2011-5-17 10:48:24

In a demographic study, the population and total income of a certain region were estimated from other data, and both estimates had lower and upper limits. At the time of the estimates, was the per capita income for the region greater than $16,500?
(1) The lower limit for the estimate of the population was 330,000 people.
(2) The lower limit for the estimate of the total income was $5,500,000,000.
题目中只告诉了人口和总收入的下限
所以不能得到人均收入的范围
如果要对题目问题进行判断
需要知道总收入下限/总人口上限才能判断出per capita income的范围

sby188 · 发表于 2011-5-17 10:50:17

How many liters of apple juice were added to the cranberry juice in a certain container?
(1) The amount of apple juice that was added was 3/2 the amount of cranberry juice in the container.
(2) There were 5 liters of cranberry juice in the container.
第二个条件单独显然不能求得答案，第一个条件，假设the amount of cranberry juice=x，则The amount of apple juice=3/2*x，条件不充足无法求出X
两个条件一起的话，因为the amount of cranberry juice=5，所以The amount of apple juice=3/2*5

-- by 会员夜夜箫歌 (2011/5/17 10:45:20)

非常感谢阿，发现自己快把数学忘光勒~~~~

上了大学以后就学了微积分，却不会这些高中的知识，惭愧，惭愧~~

急！！几道简单的数学题，求高人指点~~~

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