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简介:
加法交换律、加法结合律
①325+480+75
=325+75+480
=400+480
=880
②78+36+164
=78+(36+164)
=78+200
=278
③425+14+186
=425+(186+14)
=425+200
=625
减法的性质
①868-52-48
=868-(52+48)
=868-100
=768
②787-(87-29)
=787-87+29
=700+29
=729
③141-19-81
=141-(19+81)
=141-100
=41