按要求计算．（写出思考过程）3×40= 因为： 所以： 800×5= 因为： 所以： ．
直接写得数．+=+=﹣=+= 1﹣+= 1﹣=﹣= 1﹣﹣= 4﹣﹣= 5﹣﹣=
直接写出得数．+=+=﹣= 15﹣=
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口算高速直达.+=+= 0.32=+2=+﹣+=﹣0.25=+= 12.5×8= 2﹣﹣=﹣+=
直接写出得数．+= 1﹣= 0.32= 1﹣+=+= 5﹣=﹣= 0.75+=
+
=
+
﹣
=
+
= 1﹣
+
=
=
﹣
= 1﹣
﹣
= 4﹣
﹣
= 5﹣
﹣
=
+
=
+
=
﹣
= 15﹣
=
=
=
=
=
=
=
=
=
+
=
+
= 0.32=
+2=
+
﹣
=
﹣0.25=
+
= 12.5×8= 2﹣
﹣
=
﹣
+
=
+
= 1﹣
= 0.32= 1﹣
+
=
+
= 5﹣
=
﹣
= 0.75+
=
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