199.4X19.93-199.3x19.92
=199.4X(19.92+0.01)-199.3x19.92
=199.4X19.92+1.994-199.3x19.92
=(199.4-199.3)X19.92+1.994
=1.992+1.994
=3.986
5.4x3.8-6.5x4.4+2.7x5.4
=5.4x(3.8+2.7)-6.5x4.4
=5.4x6.5-6.5x4.4
=(5.4-4.4)x6.5
=6.5
巧算下面的题：例1：199.4X19.93-199.3x19.92 例2: 5.4x3.8-6.5x4.4+2.7x5.
3个回答
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