when a further number is added to 20 number the mean increass from 6 to 8,what is the 21st number?
问题描述：
when a further number is added to 20 number the mean increass from 6 to 8,what is the 21st number?
答
在20个数上,再加1数,平均值由6增加到8,那么第21个数是多少?
现在一共21个数,和由（20X6=120）变为（21X8=168）,很明显,第21个数是48