做一做．（1）请你试着用肢体语言表示出垂直或平行，并请同桌判断．（2）把一张纸对折两次，使折痕互相垂直．（3）把一张纸对折两次，产生三条折痕，并使折痕互相平行．
直接写出得数．×=××=÷3= 12×=+﹣+= 20÷= 18÷÷=×= 0×=×÷×=
口算 56×= 2﹣=+= 6×= 0.25×4= 57×=÷= 1÷= 21÷=÷= 1÷= 0÷=
计算下面各题．×21×÷5×÷÷÷÷24×÷8．
计算．×9=×0= 0÷=÷= 12×=×=÷=÷=
直接写得数×=÷5=×12=×=÷=÷=×= 1÷== 45×=÷2=÷=×=÷=×0=×= 1﹣=÷=×= 15÷=
×
=
×
×
=
÷3= 12×
=
+
﹣
+
=
= 18÷
÷
=
= 0×
=
×
÷
= 2﹣
=
+
= 6×
= 0.25×4= 57×
=
÷
= 1÷
= 21÷
=
÷
= 1÷
= 0÷
=
×21×
÷5×
÷
÷
÷
÷24
×
÷8．
×9=
×0= 0÷
=
÷
=
×
=
÷
=
÷
=
×
=
÷5=
×12=
×
=
÷
÷
=
×
= 1÷
=
= 45×
=
÷2=
÷
=
×
=
=
×0=
×
= 1﹣
=
÷
=
×
= 15÷
=
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