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简介:
① 加法结合律:a+b+c=a+(b+c)
25+13+87 78+29+71
=25+(13+87) =78+(29+71)
=25+100 =78+100
=125 =178
② 减法性质:a-b-c=a-(b+c)
263-55-45 189-36-64
=263-(55+45) =189-(36+64)
=263-100 =189-100
=163 =89
③ 乘法结合律:a×b×c=a×(b×c)
34×4×25 125×88
=34×(4×25) =125×8×11
=34×100 =1000×11
=3400 =11000
④ 乘法分配律:(a+b)×c=a×c+b×c;(a-b)×c=a×c-b×c
(20+4)×25 36×12+36×8
=20×25+4×25 =36×(12+8)
=500+100 =36×20
=600 =720