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巧算下面的题：例1：199.4X19.93-199.3x19.92例2:5.4x3.8-6.5x4.4+2.7x5.4要快要快要快要快要快要快要快要快要快要快要快要快要快要快要快要快
题目详情
巧算下面的题：例1：199.4X19.93-199.3x19.92 例2: 5.4x3.8-6.5x4.4+2.7x5.4
要快要快要快要快要快要快要快要快要快要快要快要快要快要快要快要快
要快要快要快要快要快要快要快要快要快要快要快要快要快要快要快要快
▼优质解答
答案和解析
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
=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
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