1. If n is positive integer and the product of all the integers from 1 to n, inclusive, is a multiple of 990, what is the least possible value of n? a）10 b) 11 c) 12 d) 13
2. If a and b are positive numbers, what are the coordinates of the midpoint of line segment CD in the xy-plane
1) The coordinates of C are (a, 1-b)
2) The coordinates of D are (1-a, b)
3. The residents of town x participated in a survey to determine the number of hours per week each resident spent watching television. The distribution of the results of the survey had a mean of 21 hours and a standard deviation of 6 hours. The number of hours that Pat, a resident of Town X, watched television last week was between 1 and 2 standard deviations below the mean. Which of the following could be the number of hours that Pat watched television last week?
a) 30 b)20 c)18 d)12 e)6
standard deviation below the mean - standard deviation能和mean不是两个东西吗？搞不太明白standard deviation作者: tkcamfan 时间: 2011-12-9 06:50
