用铁皮做一个长3米，宽0.8米，高0.5米的长方体水槽（无盖）．大约要用多少平方米的铁皮？（得数保留整平方米，用进一法取近似值）
怎样简便怎样算．++=+++=﹣（+）=
．
﹣=+=+=﹣=﹣=﹣=+=﹣= 1﹣﹣=+=
+=﹣= 7.2÷0.3=﹣1=+0.2= 0.54÷9=﹣=﹣=﹣=+= 1÷0.25=+= 0.67+0.3= 0.38×2= 8.1÷0.09= 2﹣= 12×0.5= 2.5×0.6=
计算．（能简算的要简算）﹣（+）+（﹣）．
+
+
=
+
+
+
=
﹣（
+
）=
．
﹣
=
+
=
+
=
﹣
=
﹣
﹣
=
+
=
﹣
=
﹣
=
+
=
+
﹣
= 7.2÷0.3=
﹣1=
+0.2= 0.54÷9=
﹣
=
﹣
=
﹣
=
+
= 1÷0.25=
+
= 
= 12×0.5= 2.5×0.6=
﹣（
+
）
+（
﹣
）
．
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