作图。（1）将三角形按1：3缩小（2）将长方形按2：1放大．
直接写出得数． 1﹣=+=﹣=+=+=
计算下面各题，能用简便方法的要用简便方法计算.++++ 1﹣+﹣﹣．
看谁算的又对又快．+=+=﹣= 2﹣=+=+=
直接写得数．+=﹣= 1﹣=﹣0.25= 6+=+=+=﹣= 1﹣﹣=++=．
口算：+=﹣=+3= 2.6﹣1= 5﹣=﹣=+=﹣= 2﹣﹣=+﹣= 1﹣（+）=+++=
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﹣
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1﹣
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﹣
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﹣
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﹣0.25= 6+
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﹣
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+3= 2.6﹣1
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﹣
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= 1
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