求如图空白部分面积r=5cm．
简算： 3.14×9919.25﹣0.47﹣8.531.25×0.03×8720÷45．
470÷2.5÷40．
0.8××1.25×4．
752×1.25+4.45×12.5+0.035×125．
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×1.25×4．
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