小明家要安装自来水．如果直接从自来水厂引一根管道到小明家，那么这根管道与主管道之间的夹角是多少度？请连线后用量角器量一量并标注在图中．但为了节省材料，小明家应怎样安装管道最省？请你在图中画出来．
直接写出得数． 1﹣=== 23= 52= x•x•x== a×8×b==== 4×3×25=
计算下面各题．+ 1﹣+．
直接写出得数.= 1﹣40%== 52= 1÷== 3﹣==== 0.8×÷=
看谁算得快．= 1﹣==== 1﹣=== 1﹣=== 1﹣=
怎样算简便就怎样算． ①= ②= ③= ④= ．
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= 23= 52= x•x•x=
= a×8×b=
=
=
= 4×3×25=
+
+
．
= 1﹣40%=
= 52= 1÷
=
=
=
=
=
= 0.8×
÷
=
= 1﹣
=
=
=
= 1﹣
=
=
=
=
=
= 1﹣
=
= 
= 
= 
= ．
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