6.9×(9.9+7.1)怎么巧算
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![6.9×(9.9+7.1)怎么巧算](/uploads/image/z/1033039-55-9.jpg?t=6.9%C3%97%EF%BC%889.9%2B7.1%EF%BC%89%E6%80%8E%E4%B9%88%E5%B7%A7%E7%AE%97)
6.9×(9.9+7.1)怎么巧算
6.9×(9.9+7.1)
怎么巧算
6.9×(9.9+7.1)怎么巧算
6.9×(9.9+7.1)=6.9×17
=(7-0.1)×17
=7×17-0.1×17
=119-1.7
=117.3
原式=(7-0.1)(10-0.1+7+0.1)
=(7-0.1)17
=7*17-0.1*17
=119-1.7
=117.3