现有含盐15%的盐水40千克，要把这种盐水变为含盐20%，应该怎么办？（用两种不同的思路另加2分．提示不同的思路指答案开放）
×4=×=+=×=×=÷= 0÷=×= 0×10=×=+=﹣= 0÷=÷=×4= 3×1=+=﹣= 1÷（﹣）= 4÷×4=
直接写出得数．= 16×50%= 16÷==÷3== 4÷1%= 2+1÷= 7+= 1÷=
直接写出得数． 8×=÷=×÷×= 3.6×= 15π= 80×（1﹣60%）=
直接写出得数． 21×= 1÷=÷= 8×=÷=+= 5﹣=×=
直接写出得数． ①×5= ②×= ③2﹣= ④2÷= ⑤÷1= ⑥0×= ⑦×= ⑧÷= ⑨÷21= ⑩+=
×4=
×
=
+
=
×
×
=
÷
= 0÷
×
= 0×10=
×
=
+
=
﹣
= 0÷
=
÷
=
×4=
1=
=
﹣
= 1÷（
﹣
）= 4÷
×4=
= 16×50%= 16÷
=
=
÷3=
= 4÷1%= 2+1÷
= 7+
= 1÷
=
=
÷
=
×
÷
×
= 15π= 80×（1﹣60%）=
= 1÷
=
÷
= 8×
=
÷
=
+
= 5﹣
=
×
=
×5= ②
×
= ③2﹣
= ④2÷
÷1=
= ⑦
×
= ⑧
÷
= ⑨
÷21= ⑩
+
=
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