帮我解释一下这道题吧，谢谢啦！

conanlan

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%

How many seconds will it take for a car that is traveling at a constant rate of 45 miles per hour to travel a distance of 22 yards?
            (1 mile = 1,160 yards)

A. 8

B. 9

C. 10

D. 11

E. 12

第二道题貌似挺简单的，可我怎么算都得个小数，请各位高人指点啊！

叉二

。。第一道是不是没完。。看不太懂

第二个我算也是小数=.= 同求

时间造物

第一题原题为： A certain characteristics 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%
 it is symmetric about m, 意思是 data less than m is 50% and data greater than m is also 50%. 
distribution betwen one std dev d,意思是 the distribution from m+d to m-d would also be symmetric about m and thus would contain two equal, symmetrical halves.
Thus, each of the area from m to m+d and to m-d would be 34% or 68/2=34%.

Thus, for data to be less than m+d, we have

Data from m+d to m = 34%
Data less than m = 50%
Thus, total 84%

时间造物

下面一题有错误，答案不在选项中，按照正常方法做，不用考虑选项了

conanlan

大牛大牛啊，谢谢啦！

xiaoqing508

第二题的题目正确为：How many seconds will it take for a car that is traveling at a constant rate of 45 miles per hour to travel a distance of 220 yards?       (1 mile = 1,760 yards)

 

A.      8

B.       9

C.      10

D.      11

E.       12

这样算出来是对的

T=220*60*60/（45*1760）=10