PREPA 的数学疑问

pfullsomer

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?

30, 20, 18, 12, 6


一个圆内接等腰三角形。
in the figure above,equilateral triangle ABC is inscribed in the circle. If the length of arc ABC is 24, what is the approximate diameter of the circle?
5,8,11,15,9

这道题怎么算都是靠近8啊，答案给的是11


大家帮忙解疑。。多谢

pfullsomer

Thanks so much

applejsjs

一个圆内接等腰边三角形。
in the figure above,equilateral triangle ABC is inscribed in the circle. If the length of arc ABC is 24, what is the approximate diameter of the circle?
5,8,11,15,9

这道题怎么算都是靠近8啊，答案给的是11

The arc ABC is 2/3 of the circumference of the circle.  So pai * d = 36, diameter d = 36 /3.14 =11

judyenglishS

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?

30, 20, 18, 12, 6


21 - 6 -6 = 9  So 6 is the answer since it is smaller than 9.

natalietong

没有图啊