大家一定要帮我解答，因为我马上就要考试了，谢谢！！！
1. Each employee on a certain task force is either a manager or a director. What percent of the employees on the task force are directors?(1) The average(arithmetic mean) salary of the managers on the task force is $5,000 less than the average salary of all employees on the task force.
(2) The average(arithmetic mean) salary of the directors on the task force is $15,000 greater than the average salary of all employees on the task force.
题目和给的Data是什么意思呢？不明白... ...答案是选C
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.
为什么选C呢？
3. If X is an integer, is (X^2+1)(X+5) an even number?
(1)X is an odd number
(2)each prime factor of X^2 is greater than 7.
为什么答案选D？Data(2)应该怎么理解呢？
4. If X is a posotive number less than 10, is Z greater than the average(arithmetic mean) of X and 10?
(1) On the number line, Z is closer to 10 than it is to X.
(2) Z=5X
答案是A。但是不是很理解data(2)。
请大家近来的话一定要帮忙解答，谢谢！！！ 没人给我解答吗？大家帮帮忙好吗？ post the complete question with all options here
I will do it tomorrow ....
now need sleep le 再添两道题，不好意思。
1. 9.4 9.9 9.9 9.9 10.0 10.2 10.2 10.5
The mean and the standard deviation of the 8 numbers shown are 10.0 and 0.3, respectively. What percent of the 8 numbers are within 1 standard deviation of the mean?
A. 90% B. 85% C. 80% D. 75% E. 70%
答案是D。我想了一个简单的方法就是只有8的75%是个整数，其他都不行。但是我不明白What percent of the 8 numbers are within 1 standard deviation of the mean是什么意思？
2. What is the value of xy?
(1) y=x+1
(2) y=x^2+1（x^2表示x的2次方）
答案是E。但我觉得这两个式子结合可以算出x和y的值呀，选C不对吗？ 1 numbers are within 1 standard deviation of the mean
means the number is from 10 - 0.3 to 10 + 0.3
that is 9.7 ---10.3
in the 8 numbers , 6 are in this range , so 6/8 * 100% 第三题
If X is an integer, is (X^2+1)(X+5) an even number?
(1)X is an odd number
(2)each prime factor of X^2 is greater than 7.
为什么答案选D？Data(2)应该怎么理解呢？
1,x为奇数，x+5肯定为偶数，所以，乘积肯定为偶数
2,xˇ2的质因子〉7，说明2不是其因子，也就是说xˇ2是奇数，就是说它的平方根x是奇数，X+5肯定为偶数，所以，乘积是偶数 谢谢解答，但是其他的那六道题有人会解答吗？ 2. What is the value of xy?
(1) y=x+1
(2) y=x^2+1（x^2表示x的2次方）
答案是E。但我觉得这两个式子结合可以算出x和y的值呀，选C不对吗？
算出来X的值有两个，还是不能确定唯一，所以选E 不是说了吗？
你把选项都完整的贴出来 4. If X is a posotive number less than 10, is Z greater than the average(arithmetic mean) of X and 10?
(1) On the number line, Z is closer to 10 than it is to X.
(2) Z=5X
答案是A。但是不是很理解data(2)。
Z=5X，Z-（X+10）/2=5X-（X+10）/2=（9X-10）/2
因为仅仅知道X〉0，所以上面的代数式无法得知正负，所以2是不能确定的。 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.
为什么选C呢？
由题干，p+c=60* 2/3=40
由1，c>2p ,两边同时加P，所以 3p<40
由2，P>12
得出P=13，C=27 1. Each employee on a certain task force is either a manager or a director. What percent of the employees on the task force are directors?
(1) The average(arithmetic mean) salary of the managers on the task force is $5,000 less than the average salary of all employees on the task force.
(2) The average(arithmetic mean) salary of the directors on the task force is $15,000 greater than the average salary of all employees on the task force.
题目和给的Data是什么意思呢？不明白... ...答案是选C
设manager的平均工资为M，director的平均工资为D，employee的平均工资为E，人数分别为m,d,m+d
M+5000=E D-15000=E
D-M=10000
m*M+d*D=(m+d)*E=(m+d)*(M+5000)
=mM+5000m+dM+5000d
dD-dM=5000(m+d)
d(D-M)=5000(m+d)
d/(m+d)=5000/(D-M)=5000/10000=1/2
所以可以得出。我笨的，只能用笨方法 谢谢，我下午就考试了，谢谢帮我解答！
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