含盐率为20%的盐水200克，再加入 克盐就能使含盐率提高到25%．
计算下面各题．+=﹣=+=﹣=﹣+=﹣（+）=+﹣=
+﹣﹣．
直接写出得数．+=+= 0.32= 2﹣﹣=﹣0.25=+= 12.5×8=+﹣+=
看谁算得又对又快．﹣=+=﹣= 3÷7=+=﹣= 0.8×1.5=+0.3=
直接写得数．+=﹣= 0.25×80=+0=+= 2﹣=﹣=+=
+
=
﹣
=
+
=
﹣
=
+
=
+
）=
+
﹣
=
+
﹣
﹣
．
+
=
+
= 0.32= 2﹣
﹣
=
﹣0.25=
+
= 12.5×8=
+
﹣
﹣
=
+
=
﹣
= 3÷7=
+
=
= 0.8×1.5=
+0.3=
+
=
﹣
= 0.25×80=
+
= 2﹣
=
﹣
=
+
=
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