在计算238+45+62+55时，可以简算，简算过程中最能说明简算依据的一步的算式是 ，这一步运用的运算定律是 ．
口算．×=÷5= 1÷= 15×= 1.25×=×4=÷= 1.8﹣40%= 12×（+）=×6+4×=
直接写出复数． ============
口算 21××0××12÷ 12÷ 1÷÷2÷×÷×．
计算： ①56× ②× ③12÷ ④÷．
直接写出得数．×= 2.4÷= 7﹣﹣= 0.24×50%=÷7=×37.5%= 1÷÷1=÷=×= 1÷=×9+=÷=
×
=
÷5= 1÷
= 15×
= 1.25×
=
×4=
÷
= 1.8﹣40%= 12×（
+
）=
×6+4×
=
=
=
=
=
=
=
=
=
=
=
=
×0
×
×12
÷
1÷
÷2
÷
×
×
．
②
×
③12÷
④
÷
．
×
= 2.4÷
= 7﹣
﹣
= 0.24×50%=
÷7=
×37.5%= 1÷
÷1=
÷
=
×
= 1
÷
=
×9+
÷
=
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