三年级数学天天练试题及答案2019.2.17(速算与巧算)(2)
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2018-12-25 21:36:01
【答案】
①478-128+122-72
=(478+122)-(128+72)
=600-200
=400
②464-545+99+345
=464-(545-345)+100-1
=464-200+100-1
=363