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一、计算下面各题。你认为怎样简便就怎样算。
12.5×4.12×0.8 5.7×10.1
5.6×12.3-2.3×5.6 45.9×6.7+54.1×6.7
12.5×4.12×0.8 5.7×10.1
5.6×12.3-2.3×5.6 45.9×6.7+54.1×6.7
答案
41.2 57.57 56 670
解析
12.5×4.12×0.8
=12.5×0.8×4.12
=10×4.12
=41.2
5.7×10.1
=5.7×(10+0.1)
=5.7×10+5.7×0.1
=57+0.57
=57.57
5.6×12.3-2.3×5.6
=5.6×(12.3-2.3)
=5.6×10
=56
45.9×6.7+54.1×6.7
=(45.9+54.1)×6.7
=100×6.7
=670
=12.5×0.8×4.12
=10×4.12
=41.2
5.7×10.1
=5.7×(10+0.1)
=5.7×10+5.7×0.1
=57+0.57
=57.57
5.6×12.3-2.3×5.6
=5.6×(12.3-2.3)
=5.6×10
=56
45.9×6.7+54.1×6.7
=(45.9+54.1)×6.7
=100×6.7
=670
1. 一间会议室的长是8.7m,宽是7.6m。现在要用边长是0.6m的正方形地砖铺地面,200块地砖够吗？(不考虑损耗)
答案
地砖总面积：0.6×0.6×200=72（m²），会议室的长不超过 9 m、宽不超过 8 m，会议室的面积不超过 9×8=72（m²），200 块地砖够。
解析
地砖总面积：$0.6×0.6×200 = 72\,m^2$
会议室面积：$8.7×7.6 = 66.12\,m^2$
$66.12 ＜ 72$，200块地砖够。
会议室面积：$8.7×7.6 = 66.12\,m^2$
$66.12 ＜ 72$，200块地砖够。
