31×870 12×310用简便方法怎么算?

2025-04-06 16:14:42
推荐回答(1个)
回答1:

原式
=31x870+12x310
=31x870+120x31
=31x(870+120)
=31x990
=31x1000-31x10
=31000-310
=30690