0.31×13/31×18/31×0.34
=0.31×0.13/0.31×0.18/0.31×0.34
=0.13×0.18
=0.0234啊》？？？肿么后面是0.34.。。打错了，应该是0.31，下一步没受影响恩恩谢谢~ 圣诞快乐哈~采纳是圣诞节最好的礼物。谢谢！