这是陈向东练习册里P134第23题:It the average (arithmetic mean) of x,y,z,
这是陈向东练习册里P134第23题:It the average (arithmetic mean) of x,y,z,5,and 7 is 8,which of the following must be true?II.at least one of x,y,and z is greater than 9.III.the range of the five numbers is 2 or more.答案是以上两个都对.我很郁闷,我觉得都不对啊:II.没有提示说x,y,z 都是整数,即使平均数8,必然x、y、z必然有一个大于8,可是可以小于9啊,如果可以不是整数的话.III.即使xyz都是整数,那么II就是对的,range是最大数与最小数之差么?那么最小的range也得是9-5=4,[em59]