每一次都可将黑板上所写的数加倍或者擦去它的末位数．假定一开始所写的数为458．那么，可怎样经过几次所述的变化来得到14？
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直接写出得数．== 1﹣=+0.625=== 3﹣=+0.75=
口算：+= 1.52=﹣= 1.8÷2.7=﹣=+= 4+= 3﹣=﹣=﹣=﹣﹣=++=
（1）+= （2）﹣= ．
直接写出得数．========
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=
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=
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= 1﹣
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+0.625=
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= 3﹣
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+0.75=
+
﹣
= 1.8÷2.7=
﹣
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+
= 4+
= 3﹣
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﹣
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﹣
=
﹣
﹣
=
+
+
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+
= 
﹣
= ．
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