5箱苹果一共有多少就是5个20是多少，求5个20是多少，用5×20来计算比较简单．计算20×5，可以把20看 个十， 个十乘5得 个十，即 ，所以20×5= ．
直接写出得数： 3﹣1.2=（0.1）3= 3÷1=×0.4=﹣=×7=+1= 5×÷5×=+×= 21÷3=
直接写得数．×4= 6﹣=÷=×=×=÷=÷=÷=
= 2.5== 1== 1×= 3÷1%==．
×0=×=÷=÷=
直接写得数×8=﹣=÷3= 21×= 2÷=÷=×=+=
﹣1.2=（0.1）3= 3÷1
=
×0.4=
﹣
=
×7=
+1
= 5×
÷5×
+
×
= 21
÷3=
×4= 6﹣
=
÷
=
×
×
=
÷
=
÷
=
÷
=
= 2.5
=
= 1
=
= 1
×
= 3÷1%=
=．
×0=
=
=
=
×8=
﹣
=
÷3= 21×
=
=
÷
=
×
=
+
=
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