是三年级的题目。三年级归一问题和归总问题练习。相关参考链接：http://wenku.baidu.com/link?url=_oAk9hJNGuk4Mdf1LFYmhLdig1UpGVpv13xSRGu_FvJmGTHjISe9OSG2Id0Q6V0YWEAWpZQtj_GEUqTvp7b-RAIcdwTEI3XXHwSugPY03ae
