49减7用凑十法计算
解:
49减7用凑十法计算
=49-(10-3)
=49-10+3
=39+3
=42
49-7
=(50-1)-7
=50-(1+7)
=50-8
=42
49减7用凑十法计算
=49-(10-3)
=49-10+3
=39+3
=42
49-7
=(50-1)-7
=50-(1+7)
=50-8
=42
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第1个回答 2017-10-17
=50--1-7=50-8=42