有一个三位数，个位数字为百位数字的2倍，十位数字比百位数字大1，若将此数个位与百位顺序对调（个位变百位）所得的新数比原数的2倍少49，求原数．
直接写得数.﹣=+= 3﹣=+=
请选择合适的方法计算下面各题． 1﹣﹣﹣+++﹣﹣+﹣．
直接写出得数： ①= ②= ③= ④= ⑤= ⑥= ⑦= ⑧=
直接写得数．+=+=+=﹣=+= 0.4+=﹣=﹣=+=+=
直接写出得数．= 5﹣== 0.5×0.5÷5==﹣== 0.4×25﹣10==﹣= 1+==
﹣
=
+
= 3﹣
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+
=
﹣
﹣
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+
+
﹣
﹣
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﹣
．
= ②
= ③
= ④
=
= ⑥
= ⑦
= ⑧
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+
=
+
+
=
﹣
=
+
=
=
﹣
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﹣
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=
= 5﹣
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= 0.5×0.5÷5=
=
﹣
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= 0.4×25﹣10=
=
﹣
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