计算下面各题，怎么简便就怎么算。

①0.25×0.28×40

②2.881÷0.43-0.24×3.5

③9.225÷4.5+5.5

④0.15×16×1.25

⑤0.47×3.7+6.3×0.47

⑥16.84÷2.5÷0.4