[求助]天山3上的几条数学题 3-14, 3-26, 3-34

Q14;
那道图表题横轴为number of hours,竖轴为number of menber.对应数字分别为1,2,3,4,5,6,7和9,4,1,2,,1,8,10.
      yesterday each of the 35members of a certain task force spent some time working on project P. The graph shows the number of hours and the number of members who spent that nember of hours working on the project P yesterday. what was the median number of hours that the numbers of the task force spent working on the project P yesterday.
      the choices are 2,3,4,5,6

一共35个人，median就是从小到大排最中间那个人（第18个）花了几个小时

1的9个，2的4个，3的1个，4的2个，5的1个，17个人了

那么第18个人干了6小时。所以median是6

Q34:
what is the value of the integer n?
     (1)n(n+2)=15
     (2)(n+2) 的n次方=125
答案C.我知道1的解为3或负5;可(2)的解为哪两个呢

前面有讨论，似乎应该是B答案。解为3

Q26
in the decimal representation of x ,where 0<x<1,is the tenths digit if x nonezero?
(1).16x is an integer
(2) 8x is an integer

(1)不充分，0.25*16=4，为整数，十分位不是0

                0.0625*16=1        十分位是0

(2)充分，任何正整数除以8的十分位都非0

后面两个题前面都已经讨论过了