计算．①12×÷ ②﹣× ③（+）×45 ④÷（×）⑤÷23+× ⑥×+×+ ⑦×÷× ⑧×﹣×．
简算： 3.14×9919.25﹣0.47﹣8.531.25×0.03×8720÷45．
470÷2.5÷40．
0.8××1.25×4．
752×1.25+4.45×12.5+0.035×125．
====
÷
②
﹣
×
③（
+
）×45 ④
×
）
÷23+
×
⑥
×
+
+
×
÷
×
﹣
×
．
×1.25×4．
=
=
=
=
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