9题怎么做求解答😊😊9题怎么做求解答😊😊
9题怎么做求解答😊😊体积V=25*12.5*1.2=375m³管截面S=*(D/2)²=3.14*100=314cm²=0.0314m²时间t=375/(0.0314*100)=119min