5-1/10=4.95-1/10-11/100=4.795-1/10-11/100-111/1000=4.6795-1/10-11/100-111/1000-1111/10000=4.5679……可见结果是有规律的,整数为4,小数位数与最后要减去的数的分子的数位相同,从后往前依次按照7、6、5……减小....