高校问答生态文明ppt:数学,急!!!!!!!!!!!!!!!!!!!!!!
来源：百度文库 编辑：高校问答 时间：2024/04/28 21:27:22
简便方法:
0.75 ×15+4.5×2.5
3.6×31.4+43.9×6.4
0.75 ×15+4.5×2.5
3.6×31.4+43.9×6.4
(1)0.75 ×15+4.5×2.5
=2.5×0.3×15+4.5×2.5
=2.5×4.5+4.5×2.5
=2×2.5×4.5
=5×4.5
=22.5
(2)3.6×31.4+43.9×6.4
=3.6×31.4+(31.4+12.5)×6.4
=3.6×31.4+31.4×6.4+12.5×6.4
=31.4×(3.6+6.4)+12.5×6.4
=31.4×10+12.5×8×0.8
=314+80
=394
0.75×15+4.5×2.5
=0.75×6×15÷6+4.5×2.5
=4.5×2.5+4.5×2.5
=4.5×5
=22.5
3.6×31.4+43.9×6.4
=(3.6+6.4)×31.4+12.5×6.4
=10×31.4+80
=314+80
=394
0.75 ×15+4.5×2.5
=3/4×15/1+9/2×5/2
=(换分母)5/4×9+9×5/4
=45/2
=22.5
=394