一块长方形菜地的周长是100米，长时宽的二倍，求这块长方形菜地的面积．
口算．﹣=+= 2﹣=+=﹣=﹣=++= 1﹣﹣=﹣+= 5﹣﹣=
直接写得数. 7.2÷9=﹣=+=﹣+= 5﹣=﹣×0=
= ．
直接写得数．========
﹣．
﹣
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= 2﹣
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=
﹣
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﹣
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+
+
= 1﹣
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﹣
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﹣
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﹣
=
+
=
﹣
+
= 5﹣
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﹣
= ．
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=
=
﹣
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