求助~gwd15-2，15-20

elevenjy1107

Q2:

A certain characteristic in a large population has a distribution that is symmetric about the mean m.  If 68 percent of the distribution lies within one standard deviation d of the mean, what percent of the distribution is less than m +
                d ?

 

A.    16%

B.     32%

C.     48%

D.    84%

E.     92%

请问大虾们，这个题啥意思呀~、~？

Q20:

If the sum of three integers is even, is the product of the three integers a multiple of 4 ?

(1)     All three integers are equal.

(2)     All three integers are even.

                  

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

Answer: d

假如把这个数假设为2，那不就不行吗~？答案不是e吗~？

LuckyKitten

我数学很差的，不知道对不对

Q2,就是一个分布，以m为mean,落在一个sd (m-d, m+d)中的概率是86%

所以P(x<m+d)=1-1/2(1-0.68)=0.84

Q20

先看（2）吧，如果有两个偶数必能分解出一个2*2，所以乘积一定是4的倍数

再看（1），我觉得这里（1）和（2）说的是一件事情，因为如果这三个数的和是偶数（题目条件）再加上条件1，这三个数相等，那这个数只可能是偶数，因为奇数+奇数+奇数=奇数

请指教

elevenjy1107

太感谢你了~~~~~~这数学学得真是~~~~~~刚刚的~~~~！！！！

感谢感谢~~~

我只有学习的份~~~

哪还敢指教呀~~~~嘿嘿~~~~那再帮我看一道题被~？

Q3:

If the units digit of the three-digit positive integer k is nonzero, what is the tens digit of k?

(1)     The tens digit of k + 9 is 3.

(2)     The tens digit of k + 4 is 2.

                  

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

Answer: a   谢谢谢谢~~~