一块长10分米、宽8分米的长方形铁板，把它割成一个最大的圆，面积要比原来减少百分之几？
直接写出得数．+=﹣=×2=×=÷3×÷3== 12×=×14=÷4=+÷+=
直接写得数+= 3+1.75=÷=×=×=﹣=+=×0+3= （+）×=×÷×=
口算下面各题．﹣=+=﹣= 2÷=×6=÷=×6=×=﹣=÷=÷=×=×=÷=÷= 6.4÷0.08= 4﹣2.92=÷=
直接写得数： 1﹣=×=÷2÷= 2×80%=+= 15÷= 35×=×÷×=
直接写出得数．﹣=×= 12×= 1÷=== 1.6×4×0.25= 0÷=
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= 6.4÷0.08= 4﹣2.92=
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= 15÷
= 35×
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= 1.6×4×0.25= 0÷
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